Sure! Here are the completed sentences:

1. My brother isn’t old enough to ride a motorbike. → My brother is **too young to ride a motorbike**.

2. I wasn’t tall enough to reach the book. → I **was too short to reach the book**.

3. He didn’t speak slowly enough for me to understand. → He **spoke too quickly for me to understand**.

4. Her son doesn’t study well enough to pass the exam. → Her **son studies too poorly to pass the exam**.

5. William is too fat to wear the jeans. → William **isn't thin enough to wear the jeans**.

6. David was too sick to go to work. → David **wasn't well enough to go to work**.

7. The tables were too heavy for me to lift. → The tables **weren't light enough for me to lift**.

8. She is too weak to get up. → She **isn't strong enough to get up**.

9. Mike is too young to see the horror film. → Mike **isn't old enough to see the horror film**.

10. Peter is too young to ride a bike. → Peter **isn't old enough to ride a bike**.