Determine the perpendicular distance required to lift a crate by applying a 25 Nw force which generates a torque to 100 Nw* ft.

Torque is calculated by multiplying the force apples times the length of the moment arm: . Here you have the force is 25N and the torque is 100N-Ft, so solve for R.

By the way, it's a bit unusual to mix SI units (newtons) with imperial units (feet) - are you sure these units a correct?