This is how I remember to do this. Someone will probably have a hissy fit cause there's certainly nothing "proper" about it -- it's just something that works so I can remember it.
If that were 1.015t = 4, without the exponent, you would divide both sides by 1.015 to solve for the t. So the left would cancel out to just t. And the right would be 4 divided by 1.015.
However, it's not 1.015t, it's 1.015^t so you see that's not something you can really do. What it does do is remind you to divide the 4 by 1.015, except you're going to divide the log of 4 by the log of 1.015. I have to do this to remember which to divide by which.
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