we know that
The sum of the internal angles in the triangle must be
degrees
see the attached figure with letters to better understand the problem
Step 
<u>Find the measure of the angle x</u>
In the triangle ABC

solve for x



therefore
<u>the answer Part a) is</u>
the measure of angle x is 
Step 
<u>Find the measure of the angle z</u>
we know that
--------> by supplementary angles
substitute the value of x



therefore
<u>the answer Part b) is</u>
the measure of angle z is 
Step 
<u>Find the measure of the angle y</u>
In the triangle ACD

solve for y




therefore
<u>the answer Part c) is</u>
the measure of angle y is 