Answer:
The measure of angle RST is 
Step-by-step explanation:
see the attached figure to better understand the problem
we know that
-----> equation A
-----> equation B
equate equation A and equation B




The measure of angle RST is equal to

There you go!! Hope it helps
D. x=3
I don't really know how to explain it other than the only points on the line are sitting at the x=3 and y=anything