\[\boxed{\mathbf{Вариант\ 2.}}\]
\[\boxed{\mathbf{1.}}\]
\[Ответ:\ \ \ 840.\]
\[\boxed{\mathbf{2.}}\]
\[Ответ:\ \ \ 702.\]
\[\boxed{\mathbf{3.}}\]
\[300 + 40 + 1 = 341\]
\[Ответ:\ \ \ 341.\]
\[\boxed{\mathbf{4.}}\]
\[Ответ:\ \ \ 634 < 643.\]
\[\boxed{\mathbf{5.}}\]
\[8\ сот = 800\]
\[800 - 1 = 799\]
\[Ответ:\ \ \ 799.\]
\[\boxed{\mathbf{6.}}\]
\[290 - 200 = 90\]
\[Ответ:\ \ \ 90.\]
\[\boxed{\mathbf{7.}}\]
\[278 - y = 200\]
\[y = 278 - 200\]
\[y = 78.\]
\[\boxed{\mathbf{8.}}\]
\[900 + 70 + 9 < 900 + 80 + 8\]
\[Ответ:\ \ \ 80.\]