Problem: In a general triangle ADE (as shown in the diagram) lines EB and EC are drawn. Which of the following angle relations is true?
Answer Choices:
A. x+z=a+b
B. y+z=a+b
C. m+x=w+n
D. x+z+n=w+c+m
E. x+y+n=a+b+m
Solution:
From triangle AEC x+n+y+w=180∘
From triangle BED m+a+w+b=180∘
∴x+y+n=a+b+m