plz help!! i dont know what steps to take. will be giving brainliest if u give me a step by step explanation and an answer!

Answer:
RS = 17
Step-by-step explanation:
(23-2x) + (9x-5) = 39
23-2x+9x-5 = 39
7x + 18 = 39
7x = 21
x = 3
Given: RS = 23-2x
23 - 2(3)
23 - 6 = 17