On Christmas eve, a toy shop had 80 robot cars left to sell. By the end of the day, the shop only had 17 robot cars left. How many robot cars were sold?
This is a subtraction problem because we want to know how many robot cars were taken away, or sold, from the total. We take the number of robot cars they started with, and then subtract the number of robot cars they have left to find out how many they sold.
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.