\[\boxed{\mathbf{25.}}\]
\[\textbf{а)}\ 20 - 2 \cdot 2 = 20 - 4 = 16\]
\[2 \cdot 3 + 30 = 6 + 30 = 36\]
\[40 + 2 \cdot 4 = 40 + 8 = 48\]
\[2 \cdot 5 + 50 = 10 + 50 = 60\]
\[60 + 2 \cdot 6 = 60 + 12 = 72\]
\[2 \cdot 8 - 15 = 16 - 15 = 1\]
\[\textbf{б)}\ 48 - 4 \cdot 4 = 48 - 16 = 32\]
\[69 - 3 \cdot 6 = 69 - 18 = 51\]
\[5 \cdot 3 + 53 = 15 + 53 = 68\]