David did 51 push-ups in gym class today. David did 49 more push-ups than Zachary. How many push-ups did Zachary and David do altogether?
First, we need to find how many push-ups Zachary did. We know that David did 51 push-ups and that David did 49 more push-ups than Zachary, so we can say that Zachary did 2 less push-ups than David. This means that Zachary did 51 - 2 = 49 push-ups. 

Next, we need to find how many push-ups Zachary and David did altogether. We know that Zachary did 49 push-ups and David did 51 push-ups, so we can say that Zachary and David did 49 + 51 = 100 push-ups altogether. 

Therefore the answer (numeric) is: 

100