Opposite angles of a parallelogram are equal, so:
5x - 28 = 3x - 10
2x = 18
x = 9
Plug x = 9 into the equations
m angle 2 = 5x - 28 = 5 * 9 - 28 = 17
m angle 4 = 3x - 10 = 3 * 9 - 10 = 17
The sum of all angles in a parallelogram is 360,
and we know: m angle 1 = m angle 3, so:
m angle 1 + m angle 2 + m angle 3 + m angle 4 = 360
m angle 3 + 17 + m angle 3 + 17 = 360
2 * (m angle 3) = 360 - 17 - 17 = 326
m angle 3 = 163
