Imagine an equation as a set of scales. The scales will stay in balance as long as the same operation (addition, subtraction, multiplication or division) is applied to both sides.

PEMDAS stands for parentheses, exponents, multiplication and division, and addition and subtraction. It demonstrates the right order in which to solve a math equation like this one.

One of Nathan's videos — showing him successfully calculating a lengthy equation that includes multiplication, addition, subtraction, division and even square root — gained 40,000 views ...