9. Their family (to invite) everybody to the party last week.

В задании необходимо поставить глагол to invite в форму Past Simple.

Last week - указатель на Past Simple.

Past Simple - простое прошедшее время.

To invite - правильный глагол, поэтому добавляем окончание -ed.

Предложение: Their family (to invite) everybody to the party last week. - Their family invited everybody to the party last week.

Ответ: Their family invited everybody to the party last week.