Yes. But you should really specify the unit (ounces) in the definition.
A good way to convince yourself (and us) that your equation is right is to explain in words what each side means: the amount of salt in the solution, plus the added salt, equals the amount of salt in the desired solution.
My main focus is setting up the right equation.
And, as we've seen in the time problem, the definition of variables is an essential part of "setting up the right equation" (and then interpreting the result).