@Merry Andrew,
OK, of course assuming as no one is driving the bus as that is not mentioned and assuming no chaperones, etc.
7 girls with 2 legs each (assuming these are two-legged girls) = 14 legs
Then the difficult step - couple of ways you can calculate it:
Calculate number of legs in each backpack and then calculate number of backpacks: each backpack has 56 cats (7 big cats + 49 little cats = 56). Assuming each cat has four legs 56 x 4 = 224 legs in each backpack.
Number of backpacks 49 (7 girls with 7 back packs each)
49 backpacks x 224 legs per backpack = 10,976 cat legs + 14 girl legs = 10,990 legs in total.
I do have an advantage though " I have a fourth grader so I’ve been working on word problems all year.