Question

if ab parallel to cd, cd parallel to ef and y:z=3:7 find x

Answer 1

y=3s
z=7s
ab//cd//ef 
which states that ab//ef as well..
z=x=7s
now x+y=180 {since they r co interior angles}
3s+7s=180
10s=180
s=18


x=7s=7*18=126
z=x=126
y=3*18=54

Answer 2

As AB//CD and CD //EF
Therefore, AB//CD//EF.
Angle X= angle Z (alternate interior angles are equal.

Angle X + angle Y = 180 degrees (sum of same side of transverse)
Ratio of angle Y : angle Z = 3 : 7
This is equal to ratio of angle Y : angle X
Therefore, Angle X = angle Z = (7/10) x 180
= 126 degrees.
And angle Y = (3/10) x 180= 54 degrees.