I think he will have to buy 5.6 or 6 boxes
Because i did: 3.5÷5 to get cups per serving which is .7 then i did .7×32 to get the amount of cups for 32 servings which is 22.4 then i did 22.4÷4 to get 5.6 which is the amount of boxes to buy.
I think the answer is 5.6 or 6 unless you have to round or something or you have multiple choice then that is my answer.