\[Страница\ 30.\]
\[\boxed{\mathbf{5}.}\]
\[\textbf{а)}\]
\[\textbf{б)}\]
\[\boxed{\mathbf{6}.}\]
\[\textbf{а)}\ 7 \cdot x - 46 = 38\]
\[7 \cdot x = 38 + 46\]
\[7 \cdot x = 84\]
\[x = 84\ :7\]
\[x = 12.\]
\[\textbf{б)}\ 300\ :(51 - y) = 15\]
\[51 - y = 300\ :15\]
\[51 - y = 20\]
\[y = 51 - 20\]
\[y = 31.\]
\[\textbf{в)}\ 108 - 9 \cdot y = 36\]
\[9 \cdot y = 108 - 36\]
\[9 \cdot y = 72\]
\[y = 72\ :9\]
\[y = 8.\]
\[\textbf{г)}\ 220\ :(13 + x) = 11\]
\[13 + x = 220\ :11\]
\[13 + x = 22\]
\[x = 22 - 13\]
\[x = 9.\]