Edward should buy 3 boxes because there are 30 students in your class and subtract that from 32 which is 2 so 2 students don't get. I'm not sure if this entirely accurate but I hope it helps!
8. if you need 32 valentines boxes and they come in ten then you buy 4 which is 40 total. Then, after giving all 32 students the valentines you would have 8 because 40-32=8
