David did 13 more push-ups than Zachary in gym class today. If David did 35 push-ups How many push-ups did Zachary do?
David did 13 more push-ups than Zachary. 
That means that if we start with the number of push-ups that Zachary did, and then add 13 to it, we will get the number of push-ups that David did. 

Zachary did 22 push-ups.