Ex1.

1. My dad has worked in a company since 2000

2. Those students aren't old enough to drive motorbikes

Ex2.

1. Tom wasn't hard- working so he couldn't get good marks.

2. It is dangerous to swim across this river

3. The blue dictionary isn't as expensive as the red dictionary

4. I haven't seen him since 1995

5. They hate cooking meals

6. Lan is as pretty as her sister

Ex3.

Dear Mom and Dad,
I'm having a wonderful time in Ha Long Bay.

The weather is very lovely and the beach and the islands look very beautiful.

Yesterday, I went shopping at Hon Gai Town.

I'm going to visit Dau Go Cave tomorrow.

I'm going to take photographs there.
See you soon.
Love,
Linda.

1. my dad has worked the company since 2000.

2. Those students are not old enought to drive motobikes.

EX2:

1. Tom wasn't hard working, so he couldn't get good marks.

2. It's dangerous to swim across this river.

3. the blue dictionary isn't more expensive than the red dictionary.

4. I haven't seen him since 1995.

5. they hate cooking meals.

6. lan is as pretty as her sister.