7/8 - 5/6 * 9/20

To solve the expression \( \frac{7}{8} - \frac{5}{6} \times \frac{9}{20} \), we first need to perform the multiplication before the subtraction.

1. Multiply \( \frac{5}{6} \) by \( \frac{9}{20} \): \[ \frac{5}{6} \times \frac{9}{20} = \frac{5 \times 9}{6 \times 20} = \frac{45}{120} \]

2. Simplify \( \frac{45}{120} \): The greatest common divisor of 45 and 120 is 15. \[ \frac{45 \div 15}{120 \div 15} = \frac{3}{8} \]

3. Now perform the subtraction \( \frac{7}{8} - \frac{3}{8} \): \[ \frac{7}{8} - \frac{3}{8} = \frac{7 - 3}{8} = \frac{4}{8} \]

4. Simplify \( \frac{4}{8} \): \[ \frac{4 \div 4}{8 \div 4} = \frac{1}{2} \]

The final result is: \[ \frac{1}{2} \]