\[\boxed{\mathbf{74.}}\]
\[\textbf{а)}\ 37 + 14 = 51\]
\[49 + 15 = 64\]
\[71 - 12 = 59\]
\[52 - 4 + 10 = 48 + 10 = 58\]
\[61 - 14 + 30 = 47 + 30 = 77\]
\[83 - (16 + 16) = 83 - 32 = 51\]
\[\textbf{б)}\ 34 + 58 - 86 = 92 - 86 = 6\]
\[100 - (47 + 29) = 100 - 76 =\]
\[= 24\]
\[27 - (83 - 56) = 27 - 27 = 0\]