The browser storage localStorage is not available. Either your browser does not support it or you have disabled it or the maximum memory size is exceeded. Without localStorage your solutions will not be stored.

Parentheses

Just as in mathematics, the order of operations rules are valid in JavaScript. Multiplication and division are performed before addition and subtraction. With parentheses you can specify the order of operations.
var x1 = 3 + 4 * 2;
var x2 = (3 + 4) * 2;
x1 is 11 and x2 is 14.

Exercise

Write a function mean that takes 2 numbers and returns their mean value. mean(1, 2) should return 1.5.
The mean value of two numbers
x and y is (x + y) / 2.
var mean = function(x, y) {
  return (x + y) / 2;
};