Open the brackets using Past Perfect:
We (to repair) the car by 9 p.m. yesterday.
The kids (to break) the window before their Dad came home.
They (to read) the book by yesterday's afternoon.
I (not see) him since I moved to another place.
She (to graduate) from the medical school before the 80s.
By 2000 the company (to produce) about 2,000 items.
As I approached the house I understood that I (to lose) my wallet.
The city (to change) before we visited it for the first time.
She didn't understand that she (to be) very rude with her mother.
They were glad that they (to solve) all their problems.

We (to repair) the car by 9 p.m. yesterday. → We had repaired the car by 9 p.m. yesterday.

The kids (to break) the window before their Dad came home. → The kids had broken the window before their Dad came home.

They (to read) the book by yesterday's afternoon. → They had read the book by yesterday's afternoon.

I (not see) him since I moved to another place. → I had not seen him since I moved to another place.

She (to graduate) from the medical school before the 80s. → She had graduated from the medical school before the 80s.

By 2000 the company (to produce) about 2,000 items. → By 2000 the company had produced about 2,000 items.

As I approached the house I understood that I (to lose) my wallet. → As I approached the house I understood that I had lost my wallet.

The city (to change) before we visited it for the first time. → The city had changed before we visited it for the first time.

She didn't understand that she (to be) very rude with her mother. → She didn't understand that she had been very rude with her mother.

They were glad that they (to solve) all their problems. → They were glad that they had solved all their problems.