\[\boxed{\text{4.\ 202}}\]
\[\textbf{а)} - 48 + 40 + ( - 37) =\]
\[= - (48 + 37) + 40 =\]
\[= - 85 + 40 = - 45\]
\[\textbf{б)}\ 56 + ( - 39) + ( - 7) =\]
\[= 56 + ( - 46) = 56 - 46 = 10\]
\[\textbf{в)}\ 26 + ( - 89) + 31 =\]
\[= 57 + ( - 89) = - (89 - 57) =\]
\[= - 32\]
\[\textbf{г)} - 29 + ( - 23) + 41 + 23 =\]
\[= - 52 + 64 = 64 - 52 = 12\]