Перепишите предложения в времени. Проанализируйте зависимость времени придаточного дополнительного предложения от времени главного предложения.
1. My sister says that the medicine did a lot of good to her.
2. My friend says that the doctor checked his lungs yesterday.
3. She says that he stays away from classes for three days. 4. He
says his son has a bad cough. 5. John says he has a splitting headache. 6. Mary often tells me that she does not like to call for the
doctor. 7. Tony tells me that he has all the symptoms of influenza.
8. The doctor says that he has checked her lungs. 9. Mary says
that her mother has fallen ill. 10. My brother says that he will follow the doctor's instructions. 11. She says her brother will recover
soon. 12. He says he will take a table spoonful of this mixture
three times a day before meals.

Кажется, примерно так.

1.My sister said that the medicine had done a lot of good to her.  

2.My friend said that the doctor had checked his lungs the day before.

3.She said that he stayed away from classes for three days.

4. He  said his son had a bad cough.

5. John said he had a splitting headache.

6. Mary often told me that she did not like to call for the

doctor.

7.Tony told me that he had all the symptoms of influenza.

8.The doctor said that he had checked her lungs.

9. Mary said that her mother had fallen ill.

10.My brother said that he would follow the doctor's instructions.

11. She said her brother would recover  soon.

12. He said he woud take a table spoonful of that mixture

three times a day before meals.

Объяснение:

Времена переходят в соседнее например

Present Simple-Past Simple

Present Perfect-Past Perfect

А предложения в будущем времени с will меняются на would.