Answer
36 N
Work Step by Step
$F_{1}=\frac{GMm}{r_{1}^{2}}$
$F_{2}=\frac{GMm}{r_{2}^{2}}$
$\frac{F_{2}}{F_{1}}=\frac{\frac{1}{r_{2}^{2}}}{\frac{1}{r_{1}^{2}}}=\frac{r_{1}^{2}}{r_{2}^{2}}$
$\implies F_{2}=\frac{r_{1}^{2}}{r_{2}^{2}}\times F_{1}=(\frac{r_{1}}{r_{2}})^{2}\times F_{1}$
$=(\frac{2.0\times10^{7}\,m}{3.0\times10^{7}\,m})^{2}\times80\,N=(\frac{2.0}{3.0})^{2}\times80\,N=36\,N$
