Answer:
see below and attachment
Explanation:
a=30°
because, the marked angle of 30° is an alternate interior angle to angle a. Alternate interior angles are congruent, and we know they are congruent because the 2 horizontal lines are parallel.
b=50°
because the marked angle of 50° is a vertical angle to angle b. Vertical angles are congruent because 2 lines that intersect have opposite congruent angles, making them vertical angles to each other.
c=50°
because the marked angle of 50° is a corresponding angle (same side angle) to angle c. These corresponding angles are congruent because the 2 horizontal lines are parallel.
d=100°
because the 3 interior angles of a triangle must add up to 180°. We have 30°, 50°, so the last angle must be 100°. We can also figure this out because the bottom horizontal line is a straight line, meaning the angle is also 180°. We have angle a as 30°, angle c as 50°, so angle d must be 100°.
Hope this helps! See attachment for visual.