Question 1146244
{{{x^2-9x+11x+12=180}}}


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Angles X and Y are supplementary, so the sum of their measures is 180 degrees.
Measure for angle X given as  x^2-9x.  Measure for angle Y given as 11x+12.


meas. angle X  plus meas. angle Y  is 180 degrees.
{{{(x^2-9x)+(11x+12)=180}}};
the algebra from here is straightforward.


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Clearly in the description, X is used for refering to an angle according to a point; and x is a numeric variable.     m∠x   is wrong.