Answer:
m∠1 = 75° m∠2 =45° m∠3 = 60°
Explanation:
m∠1 = 180 - { (180 - 135) + (180 - 120) }
m∠1 = 180 - { 45 + 60 }
m∠1 = 75°
The angle between 1 and 3, lets call it x, is vertically opposite to ∠2, so we must find it first to be able to get ∠2
Since a ║b
Therefore ∠x and ∠135 are co-interior angles
Therefore ∠x = 180-135
m∠x = 180 - 135
m∠x = 45°
∠2 = ∠x (Vertically opposite angles)
∠2 = 45°
Between ∠2 and ∠3 there is an angle, let's call it z.
∠z = ∠1 (Vertically opposite angles)
∠z = 75°
Since the sum of angles 2, z and 3 = 180° (Straight angle)
Therefore m∠3 = 180 - (∠2 + ∠z)
m∠3 = 180 - (45 + 75)
m∠3 = 60°
Or in a different way
∠2 + ∠z + ∠3 = 180
45 + 75 + ∠3 = 180
120 + ∠3 = 180
∠3 = 180 - 120
∠3 = 60°
Hope it helps