This is a children's problem . . .
A bus contain 7 girls.
Each girl carry 7 bags.
Inside each bag there are 7 cats.
Every cat has 7 kittens.
How many legs are in the Bus?
There are 7 girls with two legs each: 14 legs
There are bags.
There are: cats with 4 legs each: 1372 legs
There are: kittens with 4 legs each: 9604 legs
. . Add 'em up!