David did 3 push-ups in gym class today. David did 40 more push-ups than Zachary. How many push-ups did Zachary and David do altogether?
1. David did 3 push-ups in gym class today. 
2. David did 40 more push-ups than Zachary. 
3. How many push-ups did Zachary and David do altogether?

We can see that we are missing information about Zachary. We are told that David did 40 more push-ups than Zachary, but we don't know how many push-ups Zachary did. 

We can solve this problem by using what we know to figure out what we don't know. We know that David did 3 push-ups in gym class today, and we know that David did 40 more push-ups than Zachary. 

We can use this information to figure out how many push-ups Zachary did. If we add 40 to 3, we get 43. This means that Zachary did 43 push-ups in gym class today. 

Now that we know how many push-ups Zachary did, we can answer the original question. If Zachary did 43 push-ups and David did 3 push-ups, then they did a total of 46 push-ups.