\[\boxed{\mathbf{Страница}\mathbf{\ 47.}\mathbf{\ }\mathbf{Еуроки\ - \ ДЗ\ без\ мороки}}\]
\[\boxed{\mathbf{29.}}\]
\[1)\ x \cdot 18 = 100 - 46\]
\[x \cdot 18 = 54\]
\[x = 54\ :18\]
\[x = 3.\]
\[2)\ 770\ :x = 385 \cdot 2\]
\[770\ :x = 770\]
\[x = 770\ :770\]
\[x = 1.\]
\[\boxed{\mathbf{30.}}\]
\[5 \cdot a + (a - 8) =\]
\[= 6a - 8\ (рублей) - надо\ \]
\[заплатить.\]
\[При\ a = 20:\]
\[6 \cdot 20 - 8 = 120 - 8 =\]
\[= 112\ (рублей).\]
\[Ответ:112\ рублей.\]
\[\boxed{\mathbf{31.}}\]
\[707\ :7 = 11\ \ \ \ \ \ \ \ \ \ \ \ 11 \cdot 10 = 101\]
\[Неверно.\]
\[707\ :7 = 101\ \ \ \ \ \ \ \ \ 11 \cdot 10 = 110\]