The opposite angles formed on an intersecting line are equal.
Here,
angle y + 10 = angle 2y - 80
Now,
y + 10 = 2y - 80
10 + 80 = 2y - y
90 = y
Therefore,
The angle y + 10 measures 100°.
Also, angle 2y - 80 measures 100°.
The other two angles measure 80° each.
