When two parallel lines are intersected
they are called, external angles
external angles are suplementary , sum of both measures 180°
THEN
(8x + 6 ) + (9x - 30) = 180°
Now to find x
separate, isolate variable x
Then
8x + 9x = 180 - 6 + 30 = 204
17x =204
x= 204/17 = 12