Answer:
90
Step-by-step explanation:
x + 70 =120 {Exterior angle theorem}
x = 120 - 70
x = 50
y = x {Vertically opposite angles}
y = 50
z + 50 + 40 = 180 {Angle sum property}
z + 90 = 180
z = 180 - 90
z = 90
