There is a property that states that vertical angles are congruent with each other. By definition, vertical angles are opposite angles when two intersecting lines are drawn. From the figure, angle (3y - 30) is equal to angle (2x + 4). But first, let's determine x. One revolution is equal to 360°. So,
360 = 2(2x + 4) + 2(4x - 6)
Solving for x,
x = 91/3
Now, solving for y:
3y - 30 = 2x + 4
3y - 30 = 2(91/3) + 4
y = [2(91/3) + 4 + 30]/3
y = 31.56