7 boys (2 legs each) = 14 legs..............(1)

7 boys x 7 bags = 49 bags = 49 large cats

So 49 large cats have 49 x 4 legs = 196 legs ..........(2)

Each large cat has 7 small cats, so 49 large cats have 49 x 7 = 343 small cats

343 small cats have 343 x 4 legs = 1372 legs...........(3)

Adding 1 + 2 + 3 = 1582 legs........

"The power of accurate observation is commonly called cynicism by those who have not got it"