What is the force (in Newtons) used if an elevator lifts passengers 30 meters in 24 seconds and the elevator is 15,000 watts?

well... all you need to know is the definition of watts.

1 watt = (newtons*meters)/seconds = (N*m)/s

so plug in the knowns and solve for Newtons.

m=30 meters
t=24 seconds
w=15000 watts
N?
1 watt= Nm/s
15000=N*30/24
N=12000