Answer:
7A. x = 6
7B. m∠ABC = 135°
Explanation:
7A. I forget what the rule is called specifically, but the opposite angle is always congruent. So, you simply end up solving for x when you set the equation to equal 45.
7B. Use the supplementary rule, which basically states that two angles on a flat plane, when adjacent, equal 180°. So, 180 - 45 = 135.
God, my terminology is awful, but that's besides the point.