Find the missing angle

Find the measure of an angle that is 30 degrees less than its supplement.

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x = the angle
180 - x = its supplement   {supplementary angles add up to 180°} 

x = 180 - x - 30   {angle is 30° less than its supplement}
x = 150 - x   {combined like terms}
2x = 150   {added x to each side}
x = 75°   {divided each side by 2}

the angle is 75°

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