Answer:
C
Step-by-step explanation:
We know that ∠ 1 + ∠ 2 + ∠3 = 180 → (1)
and ∠ 3 + ∠ 4 = 180 → (2)
From (2) ∠ 3 = 180 - ∠ 4
Substitute ∠ 3 = 180 - ∠ 4 into (1)
∠ 1 + ∠ 2 + 180 - ∠ 4 = 180 ( add ∠ 4 to both sides )
∠ 1 + ∠ 2 + 180 = 180 + ∠ 4 ( subtract 180 from both sides )
∠ 1 + ∠ 2 = ∠ 4 → C
