Answer: Its possible I am very wrong but I think its most likely like 5 pizza boxes
because each person will have 2 slices and in each box there is 8 due to the guidelines. You can check this by doing 5(boxes) times 8(slices in each box) and it'll equal 40(number of slicers per person.
Explanation:
I did 20 times 2 which equal 40
Then divide that by 8 which equals 5