\[\boxed{\mathbf{8}\mathbf{.}}\]
\[\textbf{а)}\ 56 + 14 - 3 = 70 - 3 = 67\]
\[100 - (5 + 35) = 100 - 40 =\]
\[= 60\]
\[\textbf{б)}\ 29 + (16 - 8) = 29 + 8 = 37\]
\[73 - (4 + 19) = 73 - 23 = 50\]
\[87 - 0 + 13 = 100\]
\[91 + 0 - 25 = 66\]