Answer:
I don't know if I'm correct but the answer is 6.
Explanation:
I'm not 100% correct, but you set the other two angles to add to each other then set it equal to angle QRS and i got x=6.
Your equation should be like this: 3x + 17 + 2x +21 = 10x -1
than you solve form there
I;m not sure that this is the correct answer and maybe i'm wrong, but hope this helps