\[\boxed{\mathbf{2}\mathbf{.}\mathbf{118}}\]
\[\textbf{а)}\ 27 + 54 = 81\]
\[\textbf{б)}\ (43 + 107) - 99 =\]
\[= 150 - 99 = 51\]
\[\textbf{в)}\ 92 - 38 = 54\]
\[\textbf{г)}\ 172 - (52 + 64) =\]
\[= 172 - 52 - 64 = 120 - 64 =\]
\[= 56\]