\[\boxed{\mathbf{8.}}\]
\[\textbf{а)}\ 37 + 1 = 38\]
\[54 + 1 = 55\]
\[71 + 1 = 72\]
\[98 + 1 = 99\]
\[\textbf{б)}\ 49 + 1 = 50\]
\[89 + 1 = 90\]
\[68 + 1 + 1 = 69 + 1 = 70\]
\[79 + 1 + 1 = 80 + 1 = 81\]