Answer:
$21
Explanation:
Make the original statement into a ratio.
$28/4
Simplify the fraction above.
$28/4 = 7
So, you earn $7 per car you wash.
As a result, you multiply $7 by the number of cars the question is asking you for. In this case it is 3 cars.
So, you multiply 7 x 3
7 x 3 = 21
Therefore, you will earn $21 for washing 3 cars.