Do whatever u can no messing round plz

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

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?

The sides of a parallelogram are 24cm and 16cm. the distance between the 24cm sides is 8 cm. find the distance between the 16cm sides