letters (to sort) into the different towns usually.
The postbox (to empty) tomor­row
My question (to answer) yesterday.
Many houses (to build) in our town every year.
The mail (to load) into the train. 
His new book (to finish) next year.
Раскройте скобки, употребляя глагол в Passive Voice.  

are sorted

will be empted

was answered

are built

is loaded

will be finished

пассивный залог - это третья форма глагола, а не просто Past Simple