قاوم الخطأ

نحسب كل جداء: \( \frac{15}{7} \times \frac{11}{18} = \frac{165}{126} = \frac{55}{42} \)، و \( \frac{13}{9} \times \frac{3}{26} = \frac{39}{234} = \frac{1}{6} \). ثم \( \frac{55}{42} + \frac{1}{6} = \frac{55}{42} + \frac{7}{42} = \frac{62}{42} = \frac{31}{21} \).