If I had a six pulley system and a resistance of 24,000 N, how much effort would I need to lift it?

Suppose you could rig up a pair of pulley systems and get a friend, who is as strong as you, to pull one of them. You'd still have trouble, but you might be able to do it because each pulley would lift half the weight, or 1,000 pounds, and a quarter of that weight is 250 pounds