91Ó°ÊÓ

Here, $∠5$is supplementary to$∠4$.

If angles formed by two intersecting lines are adjacent, the two angle are said to be linear.

From the figure, $∠3$and $∠4$form a linear pair, so their sum is $180°$.

Here, $∠5$is supplementary to $∠4$it is given.

Using the definition of supplementary angles that is if two angles are supplementary then their sum is $180°$.

So, $∠5+∠4=180°$

Again $∠4+∠3=180°$

Now by substitution property,

$∠5+∠4=∠4+∠3$

Therefore, $∠5=∠3$( by subtraction property).

Therefore, $∠5$ and $∠3$ are congruent.

Here, $∠5$ is supplementary to $∠4$.

If the sum of two angles is $180°$, then they are supplementary angles.

And if angles formed by two intersecting lines are adjacent, the two angle are said to be linear.

From the figure, $∠3$and $∠4$form a linear pair, so their sum is $180°$.

The two-column proof is :

Therefore, the concept of supplementary angles and linear pairs and using substitution property, $∠5$and$∠3$ are congruent