Сократите: (9*20-9*7)/(9*23+9*3).

\[\frac{9 \cdot 20 - 9 \cdot 7}{9 \cdot 23 + 9 \cdot 3} = \frac{9 \cdot (20 - 7)}{9 \cdot (23 + 3)} =\]

\[= \frac{13}{26} = \frac{1}{2}\]