Factor the numerator to get:
(-3z(z+5))/(z+5) now you notice that (x+5) cancel out leaving:
-3z
X = 30 and <TVX is 80 degrees
Monday is the best, Thursday is 2nd best, Wednesday is 3rd best, Tuesday is 4th best.
1/4 = .25
2/4 = .50
3/4 = .75
4/4 = 1.00