The two equations are:
x = 5y - 18 (vertically opposite angles are equal)
x + y = 180 (Alternate angles , adjacent angles on a straight line)
x = 5y - 18 ---------------- (1)
x + y = 180 ---------------- (2)
From (2):
x + y = 180
y = 180 - x ---------------- Sub into (1)
x = 5(180 - x) - 18
x = 900 - 5x - 18
6x = 882
x = 147 ---------------- Sub into (2)
x = 147
y = 180 - 147 = 33
Answer: x = 147, y = 33