Hope this helps :)
Step-by-step Example 1:
Two angles are supplementary. If the measure of the angle is twice the measure of the other, find the measure of each angle.
Let the measure of one of the supplementary angles be a .
Measure of the other angle is 2 times a .
So, measure of the other angle is 2a .
If the sum of the measures of two angles is 180° , then the angles are supplementary.
So, a+2a=180°
Simplify.
3a=180°
To isolate a , divide both sides of the equation by 3 .
3a3=180°3 a=60°
The measure of the second angle is,
2a=2×60° =120°
So, the measures of the two supplementary angles are 60° and 120° .
Step-by-step Example 2:
Find m∠P and m∠Q if ∠P and ∠Q are supplementary, m∠P=2x+15 , and m∠Q=5x−38 .
The sum of the measures of two supplementary angles is 180° .
So, m∠P+m∠Q=180°
Substitute 2x+15 for m∠P and 5x−38 for m∠Q .
2x+15+5x−38=180°
Combine the like terms. We get:
7x−23=180°
Add 23 to both the sides. We get:
7x=203°
Divide both the sides by 7 .
7x7=203°7
Simplify.
x=29°
To find m∠P , substitute 29 for x in 2x+15 .
2(29)+15=58+15
Simplify.
58+15=73
So, m∠P=73° .
To find m∠Q , substitute 29 for x in 5x−38 .
5(29)−38=145−38
Simplify.
145−38=107
So, m∠Q=107° .
