If we assume that ST = 2x + 2, and that TW = 4x - 4, then we can just add the two segments together, as shown below (IF you're asking for the length, that is).
(2x + 2) + (4x - 4)
2x + 2 + 4x - 4
Group together like terms.
(2x + 4x) and (2 - 4)
6x (+) - 2
Answer: 6x - 2
