1 "Children (grow) up much too
quickly today. Girls of twelve
(dress) as if they are eighteen.'
Passive and active voice

1). Children are grown up much too  quickly today.

2). Girls of twelve  are dressed as if they are eighteen.'

Explanation:

Active voice is demonstrated as the grammatical construction in which the subject itself performs the action while in the passive voice the object and the verb act upon the subject and the subject become the recipient of the action. In the former, the subject is emphasized while in the latter the object is focused upon and showed interest in. In the given sentences, the doers of the actions are missing, and therefore, they will be filled using the rule of passive voice for present indefinite tense 'is/am/are + V3' as mentioned above.