The leas amount of large plates that would have to be purchased is 24
So the person would buy 2 packs of large plates and 3 packs of small plates.
How to: the way to find this out, is to find the first multiplication of 8 that is a number equally divided by 12. So you go:
8x1 = 8 (less than 12, so not enough)
8x2 = 16 (more than 12, but still not enough to divide equally)
8x3 = 24 (bingo!)
Hope it helps.