$\begin{align}  & {{P}_{A}}={{P}_{B}} \\  & {{\rho }_{2}}g\times 20={{\rho }_{1}}\times g\times 15 \\  & 20{{\rho }_{2}}=15{{\rho }_{1}}\to 4{{\rho }_{2}}=3{{\rho }_{1}}\to \frac{{{\rho }_{1}}}{{{\rho }_{2}}}=\frac{4}{3} \\ \end{align}$