Answer :
Given:
a.) 52 cars in 4 hours.
Let's determine how many cars did they wash in 9 hours using ratios and proportions.
We get,
[tex]\text{ 52 cars : 4 hours = x : 9 hours }\rightarrow\text{ }\frac{\text{ 52 cars}}{\text{ 4 hours}}\text{ = }\frac{x}{\text{ 9 hours}}[/tex][tex]\frac{\text{ 52 cars x 9 (hours)}}{\text{ 4 (hours)}}\text{ = }x[/tex][tex]\text{ }\frac{468\text{ cars}}{4}\text{ = x}[/tex][tex]\text{ 117 cars = x}[/tex]Therefore, they can wash 117 cars in 9 hours.