\[\boxed{\mathbf{27}\mathbf{.}}\]
\[\textbf{а)}\ 25 + 7 = 32\]
\[38 + 8 = 46\]
\[45 - 3 = 42\]
\[18 + 10 + 3 = 28 + 3 = 31\]
\[65 - 20 + 6 = 45 + 6 = 51\]
\[26 + 30 + 5 = 56 + 5 = 61\]
\[34 + 0 = 34\]
\[41 - 0 = 41\]
\[0 + 65 = 65\]
\[\textbf{б)}\ 14 - 7 + 46 = 7 + 46 = 53\]
\[78 - 0 + 15 = 78 + 15 = 93\]
\[56 + (18 - 9) = 56 + 9 = 65\]