a: \(\dfrac{25\cdot9-25\cdot17}{-8\cdot80-8\cdot10}=\dfrac{25\cdot\left(-8\right)}{-8\cdot90}=\dfrac{25}{90}=\dfrac{5}{18}=\dfrac{125}{450}\)
\(\dfrac{48\cdot12-48\cdot15}{-3\cdot270-3\cdot30}=\dfrac{-3\cdot48}{-3\cdot300}=\dfrac{4}{25}=\dfrac{72}{450}\)