Question:
In the given figure, AB || CD. Find the value of x.
Solution:
$A B \| C D$ and $\mathrm{PQ}$ is the transversal.
Then,
$\angle P E F=\angle E G H \quad[$ Corresponding Angles $]$
$\Rightarrow \angle E G H=85^{\circ}$
And,
$\angle E G H+\angle Q G H=180^{\circ}$
$\Rightarrow 85^{\circ}+\angle Q G H=180^{\circ}$
$\Rightarrow \angle Q G H=95^{\circ}$
Also,
$\angle C H Q+\angle G H Q=180^{\circ} \quad$ [Since CD is a straight line]
$\Rightarrow 115^{\circ}+\angle G H Q=180^{\circ}$
$\Rightarrow \angle G H Q=65^{\circ}$
We know that the sum of angles of a triangle is $180^{\circ}$.
$\Rightarrow \angle Q G H+\angle G H Q+\angle G Q H=180^{\circ}$
$\Rightarrow 95^{\circ}+65^{\circ}+x=180^{\circ}$
$\Rightarrow x=20^{\circ}$
$\therefore x=20^{\circ}$