You can rewrite the differential equation as

This last expression looks like the one you describe. If you solve for A instead of t, you get

This is the same as your other answer.
The way the question is written, you could have almost anything in your hand. All they have to do is add to - 12.
-14 and 2
- 11 and - 1
-12 and 0
- 82 and 70