1. My French friend finds driving on the left difficult. (USED TO)
=> My French friend isn't used to driving on the left.
2. They think the owner of the house is abroad. (THOUGHT)
=> The owner of the house is thought to be abroad.
3. We didn't go on holiday because we did not have enough money. (WOULD)
=> If we had had enough money, we would have gone on holiday.
4. The children couldn't go swimming because the sea was rough. (TOO)
=> The sea was too rough for the children to go swimming.