Explanation
The mechanical advantage (MA) of a wheel and axle is the input radius divided by the output radius. In this case, the input radius (where the effort force is being applied) is 6 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of 6 / 3 = 2.
\(M A=\frac{\text { load }}{\text { effort }} \text { so, effort }=\frac{\text { load }}{M A}=\frac{35 l b s .}{2}=17.50 \mathrm{lbs}\)