100 + x = 100 + 200

100 + x = 300

          x = 300 - 100

          x = 200 

1. Look! The boy is running in the yard.

2. He was a student last year, he studied hard.

3. I have read this book since last year.

4. Ba is ill. Will you visit him tomorrow?

5. Manh walks to school every week, today he is going by bus.