Question Video: Finding an Unknown Angle in Problems Involving Parallel Lines Mathematics • First Year of Preparatory School

Video Transcript

Work out the value of 𝑥 in the figure.

First of all, let’s think about the type of lines we’re seeing in the figure. We have two parallel lines that are cut by a transversal, which makes the 61-degree angle and the 𝑥-angle alternate interior angles. And when two parallel lines are cut by a transversal, alternate interior angles are congruent. This means both of these angles are equal in measure and 𝑥 must be equal to 61.