Two Angles are Supplementary if they add up to 180 degrees.

So (9a-9) + (9a +18) should add up to 180 degrees

9a-9 + 9a+18= 180

group similar factors together

9a+9a =180-9

18a = 171

divide by 18 both sides

a = 171/18

a = 9.5

then the first angle is 9a-9 = 9x9.5 -9= 85.5-9= 76.5 degress

then the other angle would be 180-76.5 = 103.5 degrees

## We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

- 30,000+ book summaries
- 20% study tools discount
- Ad-free content
- PDF downloads
- 300,000+ answers
- 5-star customer support

Already a member? Log in here.

Are you a teacher? Sign up now