David did 56 more push-ups than Zachary in gym class today. If David did 38 push-ups how many push-ups did Zachary and David do altogether?
First, we know that David did more push-ups than Zachary. This means that the difference between the two is positive. 

Next, we know that the difference is 56. This means that if we start with the number of push-ups that Zachary did, and we add 56, we will get the number of push-ups that David did. 

So, if we start with the number of push-ups that Zachary did, and we add 56, we will get 38. 

This means that Zachary did 38 - 56 = -18 push-ups. 

However, this is not possible, because it is not possible to do a negative number of push-ups. 

This means that our original assumption must be false, and David did not do 56 more push-ups than Zachary in gym class today.