Question :
the letter was being written by my brother when my sister came in.
* change to active voice

My brother was writting the letter when my sister came in.

Explanation:

You might want to keep this little helpful tip in mind:

Passive voice: the object is being modified/done/etc. by the subject.

→ We can see how the letter is being written by the subject.

Active voice: the subject is the one doing/modifing/etc. the object.

→ We can see how the subject is writting the letter.

Hope it helped,

BiologiaMagister

yes, they are. i think.

2b2t

explanation:

2b2t