\[\boxed{\mathbf{Стр.\ 49.\ }еуроки - ответы\ на\ пятёрку}\]
\[\boxed{\mathbf{6.}}\]
\[36 + x = 54\]
\[x = 54 - 36\]
\[x = 18.\]
\[87 - x = 30\]
\[x = 87 - 30\]
\[x = 57.\]
\[y - 18 = 29\]
\[y = 29 + 18\]
\[y = 47.\]
\[\boxed{\mathbf{7.}}\]
\[1)\ 48 = 12 \cdot 4 = 3 \cdot 16 =\]
\[= 48 \cdot 1 = 24 \cdot 2 = 6 \cdot 8\]
\[2)\ 72 = 36 \cdot 2 = 1 \cdot 72 =\]
\[= 3 \cdot 2 \cdot 12 = 8 \cdot 9 = 4 \cdot 18\]
\[\boxed{\mathbf{8.}}\]
\[84\ :(24\ :2) = 84\ :12 =\]
\[= 7\ (коробок) - потребуется\ \]
\[для\ 84\ чашек.\]
\[Ответ:7\ коробок.\]