Hi there.

This question is written so that you can understand percents using a picture.  Percent means "per 100."  So they are asking you to color so many squares per 100 of them.  In this problem you color 3 squares out of every 20.  Since there are five groups of 20 in every 100, you will end up coloring 15 squares (five groups having 3 colored squares).  This image indicates that you gave 15% of your money toward your brother's toy.

If you had a paper with 20 squares on it then you would color 3 of those squares but you have a paper with 5 times more of those squares so you would color 5 times as many or 15 squares. 3 is to 20 as 15 is to 100.