\[\boxed{\mathbf{39}\mathbf{.}}\]
\[\textbf{а)}\ 46 + 1 + 1 = 47 + 1 = 48\]
\[46 + 10 + 10 = 56 + 10 = 66\]
\[63 - 1 - 1 = 62 - 1 = 61\]
\[63 - 10 - 10 = 53 - 10 = 43\]
\[\textbf{б)}\ 77 - (11 - 1) = 77 - 10 =\]
\[= 67\]
\[100 - (11 - 10) = 100 - 1 =\]
\[= 99\]