Angle α and β are supplementary angles and when added together equal 180.
Set up an equation:
α + β = 180
β = α +30
Replace β in the first equation, to get:
α + α +30 = 180
Simplify:
2α +30 = 180
Subtract 30 from both sides:
2α = 150
Divide both sides by 2:
α = 150 /2
α = 75 degrees.
