The grocer has 58 apples in his shop. If 11 of the apples are spoilt, how many of the apples left can he sell?
This is a subtraction problem because we want to know how many good apples are left after removing the spoilt apples. We start with the number of apples and then we subtract the number of spoilt apples.
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.