Relativity Question - Time as an observer?

In the base equation [..t = to / sqrt(1 -v^2 / c^2)..] "to" is what you're solving for -- that's the time measured by the observer on Earth. "t" is what the difference in time between the stationary observer and one on the spaceship would be. Therefore, to = c*t*sqrt(c-v)(c+v)