Help me out with this Math problem?! What's a "guy wire"?

Brett needs to support a radio tower with guy wires. Each guy wire must run from the top of the tower to its own anchor 9.00m from the base of the tower. When the tower casts a shadow that is 9.00m long, Brett's shadow is 0.60m long. Brett is 1.85m tall. What is the length of each guy wire that Brett needs?