Step-by-step explanation:
due to the principle of identical angles on parallel lines when intersected by an inclined line, x is equal to the angle at B on the other side of AB.
in other words it is the supplementary angle to 150° at B.
that means together they are 180°. that is because the sum of all angles around a single point on one side of a line is 180° (because that line can be seen as the diameter of a circle, the point as the center of that circle, and one side of the diameter is a half-circle, which represents 180°).
so,
x = 180 - 150 = 30°
now, for the same principle,
x + y = 70
y = 70 - x = 70 - 30 = 40°
