How many pounds of effort force does a lever have if it has an effort arm of fifteen units long and a resistance arm of 10 units and can lift a 3-pound weight?

It would require (3 X 10)/15 = 2 lb to lift the 3 lb weight. Actually, something a little greater than that. 2 lb is the force to balance it. (Obviously, the lever "has" no force. It requires the force to lift the weight.)