Consider the below figure attached with this question.
Given:
A, B & C lie on a straight line. D, C & E lie on a different straight line.
[tex]\angle y=117^\circ,\angle z=63^\circ[/tex]
To find:
The value of x.
Solution:
A, B & C lie on a straight line.
[tex]m\angle ABD+m\angle DBC=180^\circ[/tex] (Linear pair)
[tex]y+m\angle DBC=180^\circ[/tex]
[tex]m\angle DBC=180^\circ-y[/tex]
According to the exterior angle theorem, the measure of an exterior angle of a triangle is equal to the sum of two opposite interior angles.
[tex]m\angle DBC+m\angle BDC=m\angle BCE[/tex] (Exterior angle theorem)
[tex]180^\circ-y+z=x[/tex]
[tex]180^\circ-117^\circ +63^\circ =x[/tex]
[tex]126^\circ =x[/tex]
Therefore, the value of x is 126 degrees.
