The image contains three mathematical expressions that involve fractions. Let's solve each one step by step:

1. Expression 1: $\frac{20}{7} - 8 \times \frac{1}{2}$

   First, calculate the multiplication: $8 \times \frac{1}{2} = \frac{8}{2} = 4$ Now, subtract from the fraction: $\frac{20}{7} - 4$ To subtract 4 (which is $\frac{28}{7}$ in terms of seventh fractions), find a common denominator: $\frac{20}{7} - \frac{28}{7} = \frac{20 - 28}{7} = \frac{-8}{7}$

   The result is: $\frac{-8}{7}$

2. Expression 2: $\frac{9}{15} - \frac{2}{4}$

   Simplify the fractions first: $\frac{9}{15} = \frac{3}{5} \quad \text{and} \quad \frac{2}{4} = \frac{1}{2}$ To subtract, find a common denominator (which is 10): $\frac{3}{5} = \frac{6}{10}, \quad \frac{1}{2} = \frac{5}{10}$ Now subtract the fractions: $\frac{6}{10} - \frac{5}{10} = \frac{1}{10}$

   The result is: $\frac{1}{10}$

3. Expression 3: $\frac{26}{7} - 15 \times \frac{2}{8}$

   First, calculate the multiplication: $15 \times \frac{2}{8} = 15 \times \frac{1}{4} = \frac{15}{4}$ Now, subtract this from $\frac{26}{7}$. To do this, find a common denominator (which would be 28): $\frac{26}{7} = \frac{104}{28} \quad \text{and} \quad \frac{15}{4} = \frac{105}{28}$ Subtract the fractions: $\frac{104}{28} - \frac{105}{28} = \frac{104 - 105}{28} = \frac{-1}{28}$

   The result is: $\frac{-1}{28}$

Final Results:

1. $\frac{-8}{7}$
2. $\frac{1}{10}$
3. $\frac{-1}{28}$

Would you like more details or explanations on any step? Here are some related questions:

1. How do you convert mixed numbers to improper fractions?
2. How do you find a common denominator between fractions?
3. Can you explain how to simplify fractions?
4. What is the method to add or subtract fractions with different denominators?
5. How do you multiply and divide fractions?

Tip: Always simplify fractions at the earliest opportunity to make calculations easier.