How would I set up this math equation?

Anonymous
If there's 83 million people in Iran, and 36,000 annually are converting to Christianity, how long will it take Iran to become Christian?

How would I set that problem up, without having to keep adding 36,000 until I hit 83 million. And the number of times I have to add it, is the number of years it will take for Iran to become Christian.

There has to be a simpler way to this, because that's gonna take forever.
Updates
11 mo
I did it the hard way, and it is indeed 2305 but that seems impossible. That's why I thought I set the problem up wrong to begin with.
How would I set up this math equation?
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