Problem
Assume that $m \angle 6=60^{\circ}$. What must be true about $\angle 6$ and $\angle 3$ for the lines to be parallel? Name the postulate or theorem that you used in this justification.
Solution
Step 1 ：Assume that \(m \angle 6=60^{\circ}\).
Step 2 ：For the lines to be parallel, \(\angle 6\) and \(\angle 3\) must both be \(60^{\circ}\).
Step 3 ：The postulate used in this justification is the Corresponding Angles Postulate.
Step 4 ：Final Answer: \(\boxed{\angle 6 = \angle 3 = 60^{\circ}}\)
