Question

Find mZYCD

Y
21x-7
с
100° 5x+5
E
D
A) 1199
B) 140°
C) 1230
D) 40°

Answer 1

B)140

Explanation:

So a line is=180 and the interior angles of a triangle= 180, so I did some manipulations

1. 100 + (5x+5) + <ECD = 180. But we also know that (21x-7) + <ECD=180. With some manipulation we can find that <ECD= 180 - (21x-7), so we can plug that into the other equation

2. Now: 100 + (5x+5) + (180- (21x-7))= 180

3. Solve:

105+5x+180-21x+7=180

112-16x=0

112=16x

x=7

4. Plug x=7 into 21x-7= 140