Remember, the passive voice explains an action without necessarily mentioning WHO did the action, either because we don't know, or it's not the focus of the sentence. (If you want to mention who did the action, you can add "by...." at the end.)

Active sentence: The committee selected a winner.
Passive sentence: A winner was selected (by the committee).

Passive = to be verb + past participle

In the examples on page 93, it's possible to have a passive combined with a modal. In this case, the form of the 'to be' verb is whatever generally follows that modal, either "to be" or "be":

(don't/doesn't) need to be
(don't/doesn't) have to be
should(n't) be
might (not) be
could(n't) be
can('t) be
must be
will (won't) be

Don't forget your participle after the 'to be' verb!

The dog doesn't need to be walked.

The assignment can be handwritten if you prefer.