She (read/was reading) a book, when the phone (rang/was ringing).
She WAS READING a book, when the phone RANG.
Kate (found/was finding) a coin when she (walked/was walking).
Kate FOUND a coin when she WAS WALKING.
She (brushed/was brushing) her teeth when the postman (came/was coming).
She WAS BRUSHING her teeth when the postman CAME.