What do we know?

We already have the diameter of the coin, the distance between Carol and Hamza (wich is the distance between “eye” and coin) and the distance from Earth to the Moon (wich is the distance from “eye” to the Moon).

What do we have to find out?

We'd like to work out the Moon's diameter this being twice the radius.

Work out

If you get bogged down, here you have some directions as to how to find the solution: