Hi! You need 3 boxes because if you divide 21 1/4 / 10 you get 2 1/8 or 2.125 so you at least have two boxes. You will still have some left over after the two boxes so you will need another box for those. I hope this helped, Goodluck :)
The fraction 36/180 can be recuced to 1/5 because 36 divided by 36 is 1 and 180 divided by 36 is 5 hope it helped :)
Ah well this would look like 2(30) + 30 = 90 aka 2L + W = 90
