1. If there were a screen on the window, there wouldn't be so many bugs in the room.

2.If he were not busy right now, he could help them.

3.If I were good at cooking, I could make all of my own meals.

4.If I were you, I could tell him the truth.

5.If he were a good student, he would have studied for the test 

6.If I had eaten breakfast , I wouldn't be hungry now.

7.If Mai had followed the doctor's orders, she wouldn't be sick

8.If Tom had a tickets ,he could go to the concert

9.If he wasn't bad at English, he could understand that English letter

10.If Ba were rich,he can travel around the world 

1.There are so many bugs in the room because there isn’t a screen on the window.
→ If there were a screen on the window, there wouldn't be so many bugs in the room.
2.He is busy right now so, he can’t help them.
→ If he were not busy right now, he could help them.
3.I can’t make all of my own meals because I am not good at cooking.
→ If I were good at cooking, I could make all of my own meals.
4.I’m not you, so I can’t tell him the truth.
→ If I were you, I could tell him the truth.
5.He is not a good student. He doesn’t study for the test.
→ If he were a good student, he would have studied for the test.
6.I don’t eat breakfast, so I am hungry now.
→ If I had eaten breakfast, I wouldn't be hungry now.
7.Mai is sick because she didn’t follow the doctor’s orders.
→ Mai had followed the doctor's orders, she wouldn't be sick.
8. Tom doesn’t have any tickets, so he cannot go to the concert. 
→ If Tom had tickets, he could go to the concert.
9. He is bad at English. He can’t understand that English letter.
→ If he wasn't bad at English, he could understand that English letter.
10. Ba isn’t rich. He can’t travel around the world.
→ If Ba were rich, he can travel around the world.