ok if they use 5.4 for 150 miles then you want to find out how many they use for 200 miles
5.4/150=x/200 cross multiply then divide
5.4 x 200 =1080
1080 / 150 = 7.2
they use 7.2 gallons for 200 miles
now you want to find out how many gallons for the whole trip add they amount for the first 150 miles then the amount for the last 200
5.4 + 7.2 = 12.6 gallon
12.6 is the answer
