The image shows a math exercise about finding a common denominator for fractions. Here's the breakdown:

1. The title of the exercise is: "B2. Quy đồng mẫu số", which is Vietnamese for "Finding a common denominator".
2. There are two parts:
   • a) 2 và 5: This means finding a common denominator for fractions with denominators 2 and 5.
     • The least common multiple (LCM) of 2 and 5 is 10. Therefore: $\frac{1}{2} = \frac{5}{10}, \quad \frac{1}{5} = \frac{2}{10}$
   • b) 2 và 9: This involves finding a common denominator for denominators 2 and 9.
     • The LCM of 2 and 9 is 18. Therefore: $\frac{1}{2} = \frac{9}{18}, \quad \frac{1}{9} = \frac{2}{18}$

Would you like more details on the steps or have any questions?

Here are some related questions to deepen your understanding:

1. How do you find the least common multiple (LCM) of two numbers?
2. Why is it important to find a common denominator when adding or subtracting fractions?
3. What are other methods for finding a common denominator besides using the LCM?
4. How would you find a common denominator for three or more fractions?
5. Can you simplify the fractions after finding a common denominator? When should you do that?

Tip: When finding the LCM, list the multiples of each number and look for the smallest common one.