Grace earns $7 for each car she washes. She always saves $25 for her weekly earnings. This week, she wants to have at least $65 in spending money. How many cars must wash?

In order to figure out how many cars she must wash, first you should figure out how much money total you need. This week, she needs $25 for her weekly earnings + $65 for spending money = $90. Then you divide the total amount of money, $90, by 7. The answer is 12.8, but because you can't wash 12.8 cars, the answer is 13.