Margie's car can go 32 miles on a gallon of gas, and gas currently costs 4 per gallon. how many miles can margie drive on $20 worth of gas?

Margie's car can go 32 miles on a gallon of gas and it costs 4 per gallon. You are required to find the distance in miles on Margie’s driving on 20 dollars worth of gas. You will multiply $20 worth of gas by $4 per gallon and 32 miles per gallon. The solution of the problem is as follows.  

$20 worth of gas (1 gallon of gas/ $4) ( 32 miles per gallon) =  160 miles  

Margie’s car can go 160 miles on $20 worth of gas.

The answer is something i don’t know