Question

George washed cars for four hours on Saturday in the first hour he wash four cars in the second hour he watches seven cars in the third hour HE washed 9 cars how many cars did he wash in the first three hours

Answer 1

The answer is 20. All you have to do is add all the cars he washes. So..
4+7+9=20

Answer 2

Ok so what we have to do is 4+7+9=c
4+7=11
11+9=20
c=20 
your answer is 20