For lines a and b to be parallel, the sum of angle 1 and angle 2 must equal 180 degrees.
117 + 6x-12 = 180
Simplify the left side:
105 + 6x = 180
Subtract 105 from each side:
6x = 75
Divide both sides by 6:
x = 75/6
75/6 simplifies to 25/2
The answer would be B.
