A boy spent one-half of his money for a book and one-third of his money for a pen. The remaining $2.

A boy spent one-half of his money for a book and one-third of his money for a pen. The remaining $2.25 he saved. How much money did he originally have?

Find out what percent of money was spent
Using a common denominator of 6, we have 1/2 + 1/3 = 3/6 + 2/6 = 5/6.

Therefore, 1/6 of his money is left to save. Let the boy's original money be x. We have:
x/6 = 2.25

Cross multiply, we get x = 13.50