In these sentences, you'll use the Past Simple and the Past Perfect tenses to describe actions and events that happened in the past. The Past Perfect tense (had + past participle) is used to refer to an action that occurred before another point in the past. The Past Simple tense describes actions completed at a specific time in the past.
When their mum came home last night, the children had eaten their dinner.
Here, the Past Simple tense "came" indicates the specific time the event happened last night. The Past Perfect "had eaten" indicates that the action of eating dinner was completed before their mother came home.
Yesterday I saw a woman who had been at school with my grandfather. Isn't it strange?
The Past Simple "saw" indicates the specific time (yesterday) when you saw the woman. "Had been" in the Past Perfect describes her being at school with your grandfather as a past action completed before you saw her.
It started to rain and I remembered that I had forgotten to close my bedroom window.
"Remembered" is in the Past Simple to show the action happened at a specific moment in the past, while "had forgotten" in the Past Perfect illustrates the earlier action of forgetting to close the window.
I found a book that I had never read .
The action "found" is in the Past Simple to indicate when you found the book, and "had never read" is in the Past Perfect to express that not reading the book occurred before finding it.
We tried to change the plane tickets but it was too late; they had edited the boarding pass.
"Tried" in the Past Simple shows the specific time you made the attempt, while "had edited" in the Past Perfect describes the action of editing as completed before you tried to change the tickets.