Question

They have made a plan (voice)
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Answer 1

A plan is been made by them is ur answer

hope it helps

Answer 2

Answer:

They agreed to my plan* is a sentence in simple past tense.( verb 2nd form )

For past tense the given rule is followed when changing a sentence from an active voice to a passive one:

was/were+ verb 3rd form

So the above sentence will be changed as;

My plan was agreed to by them.