D. x = 6
1) Given that we have two lines cut by a transversal one, then we can state that
these angles are Corresponding ones, i.e. they are congruent angles
2) So we can write:
12x + 3= 11x +9 Subtract 3 from the both sides,
12x +3 -3 = 11x +9 -3
12x=11x +6 Subtract 11x from both sides
12x -11x = 11x -11x +6
x=6
3) So the value for x, is x =6