If an angle measures 30°, what is its supplement? a. 20° b. 60° c. 150° d. 130°

The answer is:  [C]:  150° .

Supplementary angles, by definition, add up to 180° .

So given the measure of one angle is 30° ; the measure of its supplement angle; PLUS 30°;  must equal 180° .

So, x  +  30  = 180 ;  Solve for "x" .

 
     180  − 30 = x ;  x = 150 .

  Its supplement angle measures:  150° ;  which is answer choice:  [C] .

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