First you'll have to find the value of x.
The two labeled angles are alternate exterior which means they are congruent.
Set the equal to each other and solve for x.
3x = 4x - 24
3x - 4x = -24
-x = -24
x = -24/-1
x = 24
Now use 24 for x and find the value of angle RST.
RST = 3(24)
RST = 72
The answer is D.
Hope this helps :)