There are 7 girls on a bus.
Each girl has 7 backpacks.
Each backpack contains 7 large cats.
For each large cat, there are 7 little cats.
How many legs on the bus?
2*7 = 14 girl legs
49 back packs
49*7 = 343 large cats so 343*4 = 1372 large cat legs
343*7 = 2401 kittens so 9604 kitten legs
so then
14 + 1372 + 9604 = 10990 legs