To get angle 1, l and m intersect and there are two angles which cause vertical opposite angles. When there are vertical opposite angles, both angles have the same degree. For angle 2, you need to find angle 1 and 3, after that you deduct both angle 1 and 3 from 360° which is the angle of whole figure. 360 - 43 - 43 = 274° for angle 2 and 4, since they're also vertically opposite angles, both 2 and 4 have the same angle. All you need to do to find 2 and 4 is 274 ÷ 2 = 137°.
