$\frac{1}{R}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}+\frac{1}{{{R}_{3}}}=\frac{1}{20}+\frac{1}{30}+\frac{1}{60}=\frac{3+2+1}{6}=\frac{1}{10}\Rightarrow R=10$ $V={{V}_{1}}\Rightarrow IR={{I}_{1}}{{R}_{1}}\Rightarrow 9\times 10={{I}_{1}}\times 20\Rightarrow {{I}_{1}}=4/5A$