Answer:
32 galloons of gas.
Explanation:
In one tank, Carol's car can travel 300 miles.
There are 12 gallons in each tank.
She will be travelling 800 miles.
Let "n" be the number of tanks required. So,


Thus, the number of galloons is given by,

Thus, Carol's car will require 32 galloons of gas to travel 800 miles for visiting her grandmother.