If you lift a 24 lb. rock 5 ft. from the ground, how much work have you done?

Work is force times distance. In this case, the force is the weight of the rock so:
\(W=f \times d=24 \mathrm{lb.} \times 5 \mathrm{ft.}=120 \mathrm{ft.} \text {Ib.}\)