If you mean solve for r, as in isolate the variable, the answer is r = Ts + f
Given: T = (r-f)/s
First multiply both sides by s to get rid of the fraction.
T*s = r-f
Now move f to the left side of the equation by adding it to both sides.
Ts + f = r.
The equation you’d use to solve for r (assuming s ≠ 0) would look like this:
r = Ts + f