Answer
a. Torque = (force)(lever arm).
Torque =$(80 N)(0.25 m) = 20 N \cdot m$.
b. The torque is the same. Torque =$(F) (0.10 m) = 20 N \cdot m$.
Solve for F = 200 N.
c. Yes, the torque calculations assume that you are pushing perpendicular to the wrench handle, so that the quoted distances are the lever arms.