\[\boxed{\mathbf{2}\mathbf{.}\mathbf{210}}\]
\[6791 - 2897 = 3894\]
\[\textbf{а)}\ 2897 + 3894 = 6791\]
\[\textbf{б)}\ 6791 - 3894 = 2897\]
\[\textbf{в)}\ x - 3894 = 2897\]
\[x = 6791.\]
\[\textbf{г)}\ 6791 - x = 2897\]
\[x = 3894.\ \]