\[\boxed{\mathbf{Проверочная\ работа\ №1.\ Действие\ умножения\ смешанных\ чисел}}\]
\[\boxed{\mathbf{1.}}\]
\[\frac{39}{52} = \frac{13 \cdot 3}{13 \cdot 4} = \frac{3}{4}.\]
\[\boxed{\mathbf{2.}}\]
\[\frac{41}{16} = 2\frac{9}{16}.\]
\[\boxed{\mathbf{3.}}\]
\[1\frac{17}{19} = \frac{19 \cdot 1 + 17}{19} = \frac{36}{19}.\]
\[\boxed{\mathbf{4.}}\]
\[\frac{7}{9} \cdot 9 = 7.\]
\[\boxed{\mathbf{5.}}\]
\[3 \cdot \frac{1}{12} = \frac{3}{12} = \frac{1}{4}.\]
\[\boxed{\mathbf{6.}}\]
\[\frac{1}{4} \cdot \frac{1}{3} = \frac{1}{4 \cdot 3} = \frac{1}{12}.\]
\[\boxed{\mathbf{7.}}\]
\[\mathbf{Да.}\]
\[\boxed{\mathbf{8.}}\]
\[Нет,\ равно\ самому\ числу,\ то\ \]
\[есть\ \ равно\ \frac{7}{15}.\]