$R=\frac{V}{I}\Rightarrow R=\frac{120}{6}=20\Omega $ ${{I}_{2}}={{I}_{1}}+3=6+3=9A$ ${{V}_{2}}=R{{I}_{2}}=20\times 9=180V\Rightarrow {{V}_{2}}-{{V}_{1}}=180-120=60V$