18. A person hitting a nail with a hammer, showing a pulley system below.

Solution:

This image shows two separate actions: a hand hitting a nail with a hammer, and below it, a complex pulley system (likely a block and tackle). The hammer is a lever used to transfer force to the nail. The pulley system is designed to lift a heavy object with reduced effort.

Answer: A person is hitting a nail with a hammer, and a pulley system is shown below.