Explanation:
Hey there!
By looking through figure, l and m are parallel lines and a transversal line passes through the lines.
Now,
7x + 12° = 12x - 28°( alternate angles are equal)
12°+28° = 12x - 7x
40° = 5x
Therefore, x = 8°
Now,
12x - 28° + 9y - 77 = 180° ( being linear pair)
12×8° - 28° + 9y -77° = 180°
96° - 28° + 9y - 77° = 180°
-9 + 9y = 180°
9y = 180° + 9°
y = 189°/9
Therefore, y = 21°
Therefore, X = 8° and y= 21° .
Hope it helps....