Question

If you exert 250J of work onto a lever that is 5m long, what amount of force are you applying?

Answer 1

From the formula of W = F·d , becuase we have the values for W and d we can find F

W = F·d 
F= W/d
  = 250/5
  = 50 N

40 N of force was applied

Answer 2

We can't tell from the information you gave. Work = (force) times (distance), but that's the distance the force moves. It makes no difference how long the lever is, only how far the force moves.