How can I use the equation from problem #5 to find the answer for problem #6?

Question

5)     <!--[endif]-->Most cars can travel around 20 miles per gallon of gas that is in their tank. Write a rule that relates the total distance a car can travel d as a function of the number of gallons of gas in its tank g.

6) Using the equation from #5, how many miles can a car drive if it has 13 gallons of gas? 

Answer 1

d=20g is the equation. When g=13, d=260 miles.