\[\boxed{\mathbf{29.}}\]
\[\textbf{а)}\ 32 - 1 = 31\]
\[45 - 1 = 44\]
\[57 - 1 = 56\]
\[63 - 1 = 62\]
\[79 - 1 = 78\]
\[86 - 1 = 85\]
\[\textbf{б)}\ 30 - 1 = 29\]
\[50 - 1 = 49\]
\[70 - 1 = 69\]
\[40 - 1 = 39\]
\[80 - 1 = 79\]
\[100 - 1 = 99\]