X=70, y=55
The triangle is an isosceles triangles. In an isosceles triangle, the base angles are congruent.
Then use the triangle angle sum theorem and set the equation to 180.
55+55+x=180
110+x=180
x=70
The angle with 55 degrees and the angle with the variable y are alternate angles. Meaning they are congruent.
Answer:

And we can assume a normal distribution and then we can solve the problem with the z score formula given by:

And replacing we got:


We can find the probability of interest using the normal standard table and with the following difference:

Step-by-step explanation:
Let X the random variable who represent the expense and we assume the following parameters:

And for this case we want to find the percent of his expense between 38.6 and 57.8 so we want this probability:

And we can assume a normal distribution and then we can solve the problem with the z score formula given by:

And replacing we got:


We can find the probability of interest using the normal standard table and with the following difference:

.5x=10+.25x
.25x=10
x=40
When you buy 40 songs
The cost equals 20$