\[\boxed{\text{155.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[x \cdot 2 = 120 - 20\]
\[x \cdot 2 = 100\]
\[x = 100\ :2\]
\[x = 50.\]
\[x\ :3 = 60 + 30\]
\[x\ :3 = 90\]
\[x = 90 \cdot 3\]
\[x = 270.\ \]