What number do we want the denominator to reduce to?

Does anyone know how to do geometryme with this problem

Mis the midpoint of rq if rm equals 2x + 5 and mq equals 4x - 9 what is the length of rq

Cal's go cart has a gas tank with the dimensions shown below. he uses a gas can that holds 11 gallon of gas, to fill the go cart tank. 11 gallon = 231 inches^3 how many full gas cans will it take to fill the go cart's gas tank?