\[\boxed{\mathbf{773\ (773)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[a + b - c\]
\[\textbf{а)}\ a = - 3;\ \ b = - 15;\ \ c = - 27:\]
\[a + b - c = - 3 + ( - 15) - ( - 27) = - 3 - 15 + 27 = - 18 + 27 = 9.\]
\[\textbf{б)}\ a = - 65;\ \ b = 15;\ \ c = - 50:\]
\[a + b - c = - 65 + 15 - ( - 50) = - 65 + 15 + 50 = - 65 + 65 = 0.\ \]