The probability that the light is red on exactly 7 days

Which point on the x-axis lies on the line that passes through point c and is parallel to lino ab?

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?