Jimmy Cricket has 21 movies he wants to see this month. He has already seen 12 of them. How many movies does he have left to see this month?
This is a subtraction problem because we want to know how many movies Jimmy Cricket has left to see this month. We take the total number of movies that he wants to see this month, and then we subtract the number of movies that he has already seen.
The keywords to look out for in a problem involving subtraction are: take away; how many more; how many less; how many left; greater; smaller.