Прошу помогите решить задание по английскому и по возможности обьяснить как это делается.

Помочь - помогу, а вот объяснить, как это делается, увы - это тема не одного урока и даже не пяти.. .

1) I (had worked) at the Department Store before I (was hired) as Sales Manager by your firm.
2) Your proposals (will have been studied) by our designers before they (present) THEM to the next meeting of Research and Development Department.
3) The advertisement of our new smoking device (was shown) over TV yesterday.
4) Consumer demands (are met) by the equipments produced by Japanese company.
5) Booklets advertising excursions abroad can (be seen) in many bookshops of the town.
6) Some subsidiaries of Sumsung company (are located) in our town.
7) We can`t (buy) new fish gutting equipment now because we (are) short of money.
8) To increase our turnover we (are promoting) now our new model of fish-gutting equipment.
9) One of our subsidiaries (is based) in Singapore, the other (has) its headquarter in Taiwan. They both (began) their activity 5 years ago.
10) The accounts (are) usually CHECKED every month by the chief accountant.

PS Вот вам в помощь таблицы видо-временных форм английского глагола в действительном и страдательном залогах - поможет разобраться, что к чему!
http://www.alleng.ru/mybook/5verb.htm