If line PQ bisects with Line ST at R. SR = 3x +3 and ST = 30 Find x

Question

I come up with x being 9 to equal 15 but the choice for answers are:
x=8
x=6
x=4
x=2
What am I doing wrong?

Answer 1

since R is the midpoint of ST, SR is 1/2 ST, so

2(3x+3) = 30
3x+3 = 15
3x = 12
x = 4

not sure what you mean by

x being 9 to equal 15

Answer 2

PQ⎯⎯⎯⎯⎯ bisects ST⎯⎯⎯⎯⎯ at R. SR=3x+3 and ST=30. Find x.