To solve this problem, we need to know that the adjacent interior angles (2 and 5, or 3 and 4) between two parallel lines are supplementary.
This means that ∠2+∠5 = 180 °
which means
x+50 + 4x+30 = 180
collect similar terms and solve
5x + 80 = 180
5x = 180-80 = 100
x=20 °
∠2 = x+50 = 20+50 = 70 °
But ∠ 1 = ∠ 2 (vertical angles)
therefore
∠ 1 = 70 °
