diff --git a/src/exo3/exo3.test.ts b/src/exo3/exo3.test.ts
new file mode 100644
index 0000000..ecc2375
--- /dev/null
+++ b/src/exo3/exo3.test.ts
@@ -0,0 +1,104 @@
+import * as Option from 'fp-ts/lib/Option';
+
+import {
+  sortStrings,
+  sortNumbers,
+  sortNumbersDescending,
+  sortOptionalNumbers,
+  sortPersonsByName,
+  sortPersonsByAge,
+  sortPersonsByAgeThenByName,
+} from './exo3';
+
+describe('exo3', () => {
+  describe('sortStrings', () => {
+    it('should return an alphabetically sorted array of strings', () => {
+      const strings = ['xyz', 'aba', 'ori', 'aab', 'ghl'];
+
+      const result = sortStrings(strings);
+      const expected = ['aab', 'aba', 'ghl', 'ori', 'xyz'];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortNumbers', () => {
+    it('should return a sorted array of numbers', () => {
+      const numbers = [1337, 42, 5701];
+
+      const result = sortNumbers(numbers);
+      const expected = [42, 1337, 5701];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortNumbersDescending', () => {
+    it('should return a sorted array of descending numbers', () => {
+      const numbers = [1337, 42, 5701];
+
+      const result = sortNumbersDescending(numbers);
+      const expected = [5701, 1337, 42];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortOptionalNumbers', () => {
+    it('should return a sorted array of optional numbers', () => {
+      const optionalNumbers = [Option.some(1337), Option.none, Option.some(42)];
+
+      const result = sortOptionalNumbers(optionalNumbers);
+      const expected = [Option.none, Option.some(42), Option.some(1337)];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortPersonsByName', () => {
+    it('should return an array of persons alphabetically sorted by their name', () => {
+      const alice = { name: 'Alice', age: Option.none };
+      const bob = { name: 'Bob', age: Option.none };
+      const crystal = { name: 'Crystal', age: Option.none };
+
+      const persons = [crystal, alice, bob];
+
+      const result = sortPersonsByName(persons);
+      const expected = [alice, bob, crystal];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortPersonsByName', () => {
+    it('should return an array of persons sorted by their age', () => {
+      const alice = { name: 'Alice', age: Option.some(42) };
+      const bob = { name: 'Bob', age: Option.none };
+      const crystal = { name: 'Crystal', age: Option.some(29) };
+
+      const persons = [crystal, alice, bob];
+
+      const result = sortPersonsByAge(persons);
+      const expected = [bob, crystal, alice];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+
+  describe('sortPersonsByName', () => {
+    it('should return an array of persons sorted first by age and then by name', () => {
+      const alice = { name: 'Alice', age: Option.some(42) };
+      const bob = { name: 'Bob', age: Option.none };
+      const crystal = { name: 'Crystal', age: Option.some(29) };
+      const dorian = { name: 'Dorian', age: Option.some(29) };
+      const edgar = { name: 'Edgar', age: Option.none };
+
+      const persons = [dorian, alice, edgar, bob, crystal];
+
+      const result = sortPersonsByAgeThenByName(persons);
+      const expected = [bob, edgar, crystal, dorian, alice];
+
+      expect(result).toStrictEqual(expected);
+    });
+  });
+});
diff --git a/src/exo3/exo3.ts b/src/exo3/exo3.ts
new file mode 100644
index 0000000..3b97f2e
--- /dev/null
+++ b/src/exo3/exo3.ts
@@ -0,0 +1,59 @@
+// `fp-ts` training Exercice 3
+// Sort things out with `Ord`
+
+import * as Option from 'fp-ts/lib/Option';
+
+import { unimplemented } from '../utils';
+
+///////////////////////////////////////////////////////////////////////////////
+//                          SORT PRIMITIVE TYPES                             //
+///////////////////////////////////////////////////////////////////////////////
+
+export const sortStrings: (
+  strings: ReadonlyArray<string>,
+) => ReadonlyArray<string> = unimplemented;
+
+export const sortNumbers: (
+  numbers: ReadonlyArray<number>,
+) => ReadonlyArray<number> = unimplemented;
+
+///////////////////////////////////////////////////////////////////////////////
+//                                REVERSE SORT                               //
+///////////////////////////////////////////////////////////////////////////////
+
+export const sortNumbersDescending: (
+  numbers: ReadonlyArray<number>,
+) => ReadonlyArray<number> = unimplemented;
+
+///////////////////////////////////////////////////////////////////////////////
+//                            SORT OPTIONAL VALUES                           //
+///////////////////////////////////////////////////////////////////////////////
+
+export const sortOptionalNumbers: (
+  optionalNumbers: ReadonlyArray<Option.Option<number>>,
+) => ReadonlyArray<Option.Option<number>> = unimplemented;
+
+///////////////////////////////////////////////////////////////////////////////
+//                           SORT COMPLEX OBJECTS                            //
+///////////////////////////////////////////////////////////////////////////////
+
+export interface Person {
+  readonly name: string;
+  readonly age: Option.Option<number>;
+}
+
+export const sortPersonsByName: (
+  person: ReadonlyArray<Person>,
+) => ReadonlyArray<Person> = unimplemented;
+
+export const sortPersonsByAge: (
+  person: ReadonlyArray<Person>,
+) => ReadonlyArray<Person> = unimplemented;
+
+///////////////////////////////////////////////////////////////////////////////
+//                          COMBINE SORTING SCHEMES                          //
+///////////////////////////////////////////////////////////////////////////////
+
+export const sortPersonsByAgeThenByName: (
+  person: ReadonlyArray<Person>,
+) => ReadonlyArray<Person> = unimplemented;
diff --git a/src/exo3/index.ts b/src/exo3/index.ts
new file mode 100644
index 0000000..756b59b
--- /dev/null
+++ b/src/exo3/index.ts
@@ -0,0 +1 @@
+export * from './exo3';