diff --git a/08_calculator/calculator.spec.js b/08_calculator/calculator.spec.js
index 3507452..7cd2314 100644
--- a/08_calculator/calculator.spec.js
+++ b/08_calculator/calculator.spec.js
@@ -2,55 +2,55 @@ const calculator = require('./calculator');
 
 describe('add', () => {
 	test('adds 0 and 0', () => {
-		expect(calculator.add(0,0)).toBe(0);
+		expect(calculator.add(0, 0)).toBe(0);
 	});
 
 	test.skip('adds 2 and 2', () => {
-		expect(calculator.add(2,2)).toBe(4);
+		expect(calculator.add(2, 2)).toBe(4);
 	});
 
 	test.skip('adds positive numbers', () => {
-		expect(calculator.add(2,6)).toBe(8);
+		expect(calculator.add(2, 6)).toBe(8);
 	});
 });
 
 describe('subtract', () => {
 	test.skip('subtracts numbers', () => {
-		expect(calculator.subtract(10,4)).toBe(6);
+		expect(calculator.subtract(10, 4)).toBe(6);
 	});
 });
 
 describe('sum', () => {
-	test.skip('computes the sum of an empty array', () => {
-		expect(calculator.sum([])).toBe(0);
+	test.skip('computes the sum of an empty parameter', () => {
+		expect(calculator.sum()).toBe(0);
 	});
 
-	test.skip('computes the sum of an array of one number', () => {
-		expect(calculator.sum([7])).toBe(7);
+	test.skip('computes the sum of one number', () => {
+		expect(calculator.sum(7)).toBe(7);
 	});
 
-	test.skip('computes the sum of an array of two numbers', () => {
-		expect(calculator.sum([7,11])).toBe(18);
+	test.skip('computes the sum of two numbers', () => {
+		expect(calculator.sum(7, 11)).toBe(18);
 	});
 
-	test.skip('computes the sum of an array of many numbers', () => {
-		expect(calculator.sum([1,3,5,7,9])).toBe(25);
+	test.skip('computes the sum of many numbers', () => {
+		expect(calculator.sum(1, 3, 5, 7, 9)).toBe(25);
 	});
 });
 
 describe('multiply', () => {
 	test.skip('multiplies two numbers', () => {
-		expect(calculator.multiply(2,4)).toBe(8);
+		expect(calculator.multiply(2, 4)).toBe(8);
 	});
 
 	test.skip('multiplies several numbers', () => {
-		expect(calculator.multiply(2,4,6,8,10,12,14)).toBe(645120);
+		expect(calculator.multiply(2, 4, 6, 8, 10, 12, 14)).toBe(645120);
 	});
 });
 
 describe('power', () => {
 	test.skip('raises one number to the power of another number', () => {
-		expect(calculator.power(4,3)).toBe(64); // 4 to third power is 64
+		expect(calculator.power(4, 3)).toBe(64); // 4 to third power is 64
 	});
 });
 
diff --git a/08_calculator/solution/calculator-solution.js b/08_calculator/solution/calculator-solution.js
index ab39a60..b6b7cf7 100644
--- a/08_calculator/solution/calculator-solution.js
+++ b/08_calculator/solution/calculator-solution.js
@@ -6,8 +6,8 @@ const subtract = function (a, b) {
   return a - b;
 };
 
-const sum = function (array) {
-  return array.reduce((total, current) => total + current, 0);
+const sum = function (...args) {
+  return args.reduce((total, current) => total + current, 0);
 };
 
 const multiply = function(...args){
diff --git a/08_calculator/solution/calculator-solution.spec.js b/08_calculator/solution/calculator-solution.spec.js
index 453707c..c99993b 100644
--- a/08_calculator/solution/calculator-solution.spec.js
+++ b/08_calculator/solution/calculator-solution.spec.js
@@ -21,30 +21,30 @@ describe('subtract', () => {
 });
 
 describe('sum', () => {
-  test('computes the sum of an empty array', () => {
-    expect(calculator.sum([])).toBe(0);
+  test('computes the sum of an empty parameter', () => {
+    expect(calculator.sum()).toBe(0);
   });
 
-  test('computes the sum of an array of one number', () => {
-    expect(calculator.sum([7])).toBe(7);
+  test('computes the sum of one number', () => {
+    expect(calculator.sum(7)).toBe(7);
   });
 
-  test('computes the sum of an array of two numbers', () => {
-    expect(calculator.sum([7, 11])).toBe(18);
+  test('computes the sum of two numbers', () => {
+    expect(calculator.sum(7, 11)).toBe(18);
   });
 
-  test('computes the sum of an array of many numbers', () => {
-    expect(calculator.sum([1, 3, 5, 7, 9])).toBe(25);
+  test('computes the sum of many numbers', () => {
+    expect(calculator.sum(1, 3, 5, 7, 9)).toBe(25);
   });
 });
 
 describe('multiply', () => {
   test('multiplies two numbers', () => {
-    expect(calculator.multiply([2, 4])).toBe(8);
+    expect(calculator.multiply(2, 4)).toBe(8);
   });
 
   test('multiplies several numbers', () => {
-    expect(calculator.multiply([2, 4, 6, 8, 10, 12, 14])).toBe(645120);
+    expect(calculator.multiply(2, 4, 6, 8, 10, 12, 14)).toBe(645120);
   });
 });