It’s d because u need to know how to divide
Answer:
Is just a letter identifying the angle.
Since,Angles of a triangle sum up to 180 ,u add both the given numbers and subtract it from 180
Consider,

. Let's say

then the problem reduces to

. (Do you understand this step?)
So then replacing a again with our definition we get,

.
x = 20 - -5 = 20 + 5 = 25
y = 16 - 1 = 15
<h2>
x = 25</h2><h2>
y = 15</h2>