Question

letters are being posted change into passive ​

Answer 1

The voice of the given sentence can be changed as shown below:

They are posting letters.

Explanation

This is a object implied case. An object implied sentence in active-passive voice is a sentence that is passive but the object is missing. While converting it into active we have to provide the object from our side. This sentence is already passive. So we provided the object ‘them’ from our side. With object the sentence would look as follows:

Letters are being posted by them. (Passive)

They are posting letters. (Active)