Answer:
B. A and C
this correct because they both have 3 at the bottom
You must try to remove one of the unknown variables from the system by multiplying one in a way that when adding (or subtracting) one to another “makes it disappear” and so whatever value you get can be substituted back in to get the other unknown!
Here you go the answer is 32.5 gallons by each car. Hope that helped!