Do you mean solve
(In)(y)=(k)(t) for y?
If so then all you do is divided (In) on both sides and you'll get
Y=(k)(t)/(In)
The basic thing you need to know when solving for a variable is that you want to make it isolated.
On the other-hand, if you meant how do you solve for y=(k)(t) for y, then it's already solved.