# Consecutive Interior Angles: in Parallel Lines

How to solve the consecutive interior angles in parallel lines: formula, 1 example, and its solution.

## Consecutive Interior Angles

By two lines and a transversal,

two pairs of consecutive interior angles are formed.

∠1 and ∠2

∠1' and ∠2'

## Formula

Consecutive interior angles in parallel lines

are supplementary.

m∠1 + m∠2 = 180

m∠1' + m∠2' = 180

## Example

Solution

Solution (Detail)

The given angles are

consecutive interior angles in parallel lines.

So the given angles are congruent.

So [5x + 60] + [70] = 180.

+60 + 70 = +130

Move +130 to the right side.

Then 5x = 50.

Divide both sides by 10.

Then x = 5.

So x = 5.