It is important to remember that Vertical angles are defined as two non-adjacent angles formed by intersecting lines. These angles share the same vertex and they are congruent.
Observe the figure attached. Since lines "a" and "b" are parallel, you can notice that the angle 82° angle x° are Vertical angles. Therefore, they are congruent.
The total number of points scored on the test woukd be 200. the independent variable would be x, or the number of questions answered correctly. the dependent would be the points scored because the points scored depends on how good you did on the test.