Answer: a ∥ b (given)
m∠1 + m∠3 = 180° (Linear Pair Theorem)
m∠5 + m∠6 = 180° (Linear Pair Theorem)
m∠1 + m∠3 = m∠5 + m∠6 (Corresponding Angles Postulate)
m∠3 = m∠6 (Subtraction Property of Equality)
m∠1 = m∠5 (Subtraction Property of Equality)
Explanation: