Aitch.

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

A strike was thrown in ten pin bowling.

Xylophone.

River.

She was reading braille.

A pea.

A gummy bear.

80
(21 / 7) + (9 * 10) - 13 = 3 + 90 - 13 = 80

A bullet.

An onion.

DonKey.