1. Mr. Tam said to her that she would be very busy the following day.

(reported speech : will be --> would be, tomorrow --> the following day)

2. Hoa said that she had to finish her homework then.

(reported speech : must + Vinf --> had to + Vinf, now --> then)

3. Lan asked me if I had a car.

(reported speech question : asked + S + if,

present simple "do you have" --> past simple "I had"

`1.`Mr Tam said to her that she would be very busy the following day.

`=>`Form : S + said to O ( that ) + S + V lùi thì...

`-`I `->`She ( Đổi ngôi )

`-`will `->`would ( Lùi thì )

`-`tomorrow `->`the next day/the following day ( Chuyển đổi thời gian )

`2.`Hoa said to me that she had to finish her homework then.

`=>`Form : S + said to O ( that ) + S + V lùi thì...

`-`I `->`She ( Đổi ngôi )

`-`must `->`had to

`-`my `->`her

`-`now `->`then

`3.`Lan asked me if I had a car.

`=>`Cấu trúc câu gián tiếp với câu hỏi Yes/No Questions : S + asked/ wondered/ wanted to know + if/whether + S + V lùi thì

`-`You `->`I ( Đổi ngôi )

`-`do...have `->`had ( Lùi thì )