Adam, my cousin, has invited 28 of his friends to a party. 10 of his friends could not come. How many of his friends were able to come to his party?
This is a subtraction problem because we want to find out how many of Adam’s friends were able to come to his party. We take the total number of people that were invited which is 28, and then we subtract the number of people that did not come.
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.