A plant

Boobs.

there's a grandfather, a father and a son

25

A carrot

To blend in with its surroundings.

Eleven

Of course it is. A $100 bill is worth more than a $1 bill (newer one).

You passed with flying "collars"

Because Louis is 5 days older than Martha!

Let x be the distance in which B catches up with A.

Now time taken by A will be 3 hours more than B.

x/4 = x/20 + 3
x/4 - x/20 = 3
4x/20 = 3
x/5 = 3
x = 15 km

Chicken.