Answer:
Mitch will need to buy 22 packs.
Explanation:
My favorite thing to do in these kinds of equations is to multiply 4 times the choices im given. In this case multiplying 4 and 22 gives us 88. Even though this is a bit too much, buying 20 packs will only give us 80, buying 21 will give us 84, and buying 23 will give us 92 which is far too many.