Step-by-step explanation:
when 2 lines intersect, the angles on both sides of either one of the lines midst be the same, of course (where would other angles come from ? we are dealing with straight lines). they are only left-right mirrored.
therefore,
5x = 3x + 60
2x = 60
x = 30
so, both angles are 5×30 = (3×30 + 60) = 150°
