\[\boxed{\mathbf{2}\mathbf{.}\mathbf{109}}\]
\[\textbf{а)}\ (5223 + 1687) - 587 =\]
\[= 5223 + (1687 - 587) =\]
\[= 5223 + 1100 = 6323\]
\[\textbf{б)}\ (2734 + 437) - 2634 =\]
\[= (2734 - 2634) + 437 =\]
\[= 100 + 437 = 537\]
\[\textbf{в)}\ 87\ 844 - (87\ 244 + 270) =\]
\[= (87\ 844 - 87\ 244) - 270 =\]
\[= 600 - 270 = 330\]
\[\textbf{г)}\ (7694 + 2306) - 888 =\]
\[= 10\ 000 - 888 = 9\ 112\]