Find the values of x and y for which the quadrilateral must be a parallelogram. I tried on this but i don't think i am right

an

y = 6x -3y -12

y +3y +12 = 6x

=> . x = { 2y / 3 +2 } this is equation of line in terms of x

=> . if line meets the x-axis the co-ordinates of meeting point would be ( x , 0 )

=> . x = 2 ( 0 ) / 3 + 2

=> . x = 2

so, the point is ( 2 , 0 )

the answer is d.x= 90°

y= 50°

arc lm= 100°

i got this one chief

the answer to that one is b