I believe the correct answer is D.
Answer:
The value of the test statistic is 
Step-by-step explanation:
The formula for the test statistic is:

In which X is the statistic,
is the mean,
is the standard deviation and n is the number of observations.
In this problem, we have that:

So



The value of the test statistic is 
2x =50 since it is an isosceles triangle
x =25
the sum of all angles in a triangle is 180
5y + 10 + 50 + 2x=180
5y + 10 + 50 +50 =180 because 2x = 50
combine like terms
5y +110 = 180
subtract 110 from each side
5y = 70
y = 14