If extend the line by the 50° and 90°, you form a triangle. They're alternate interior angles so the angle outside of the triangle at the left of the bottomost line is congruent to 150°. You then can subtract that from 180° to get the angle inside the triangle that's next to it, which gives you 30°. The 90° is also on the same like as one of the angles inside of the triangle, meaning together the two should equal 180°, making the angle inside the triangle 90° also. You then have 2 of the triangle's angles and can subtract the sum of them from 180° to get the 3rd angle of it (60°). That 3rd angle is on the same line to x, so 180°-60° should give you x, making x 120°, I think.