I'm not very good with this sort of thing, but I would say 0. The riddle says the girls are *on* a bus...the question asks for legs* in*the bus. Maybe I'm trying too hard.... There are 7 girls *on* a bus Each girl has 7 backpacks In each backpack, there are 7 big cats For every big cat there are 7 little cats Question: How many legs are there *in* the bus?