20 quest at a party 8 gallon of punch estimate each guest will drink 2 cups how much punch will be left

First you need to know how many cups are in a gallon there is 16 cups in 1 gallon that means you need to multiply 8 x 16 which equals 128 
then you have to multiply 20 x 2 which equals 40
now you have one last step you have to subtract 128 - 40 which equals 88
88 is your answer 
 
 Hope this helps :)