Determine the force required to raise the weight:

Free Body Diagram:
Hint 2
The Free Body Diagram at the second pulley:
First, draw the Free Body Diagram:
Since the 20 lb weight acts downwards, two (2) 10 lb forces must counter act upwards. Next, draw another FBD at the second pulley.
If 10 lbs is acting on one end, then 10 lbs must be acting on the other side. Therefore, you'd need to apply 10 lbs of force to raise the weight through the pulley system.
10 lbs