\[\boxed{\mathbf{2}\mathbf{.}\mathbf{189}}\]
\[\textbf{а)}\ n + 6775\]
\[n = 657:\]
\[675 + 6775 = 7450.\]
\[n = 4315:\]
\[4315 + 6775 = 11\ 090.\]
\[\textbf{б)}\ 41\ 942 - z\]
\[z = 39\ 761:\]
\[41\ 942 - 39\ 761 = 2181.\]
\[z = 21\ 942:\]
\[41\ 942 - 21\ 942 = 20\ 000.\]
\[\textbf{в)}\ (c + d) - 763\]
\[c = 720;\ \ d = 382:\]
\[(720 + 382) - 763 =\]
\[= 1102 - 763 = 339.\]
\[c = 7112;\ \ d = 905:\]
\[(7112 + 905) - 763 =\]
\[= 8017 - 763 = 7254.\ \]