As a student, Superman sold advertising space in the Daily Planet newspaper. His income was a base salary of $, and in addition he got a % commission on his sales. How much would Superman make in a month if he sold $ worth of advertising space?
In this case you need to know the base salary and the commission. Then you add the two numbers together. The text tells us his base salary is $. So you need to figure out what his commission is for the advertising space he sold3.
Superman’s total income then becomes:
Superman made $