You haven't given us the whole problem.
The equation tells the relationship between 's' and 't' .
Now the question has to be either
"Find 's' at a certain 't' .",
or else it has to be
"Find the 't' that produces a certain 's'."
You gave us the equation that we'll use to answer the question,
but you never actually gave us the question.
I suspect that the question might be "What is 't' when 's' is 200 ?"
But I'm not going to put a lot of work into it until I know for sure.
(Not for 5 points, that's for sure.)