When I was ten, I started playing cricket. (make it simple)

Complex: When I was ten, I started playing cricket.
Simple: At the age of ten, I started playing cricket.

• When যুক্ত Complex Sentence কে Simple Sentence করার নিয়ম:
- When উঠে যায় এবং when এরপরের অংশে যে Subject ও Verb থাকে টা উঠে যায়।
- ছোট সময় বুঝালে at/ in বসে।
- ঋতু বুঝালে তার পূর্বে in বসে।
- বয়স বুঝালে at the age of বসে।
- Comma (,) এরপরের অংশ বসবে।

Similar examples:
- Complex: When it was evening, I saw the children playing in the field.
- Simple: At evening I saw the children playing in the field.
- Complex: When it is winter, we usually eat pithas.
- Simple: In winter, we usually eat pithas.

Source: Advanced Learner's Communicative English Grammar and Composition by Chowdhury and Hossain.