To determine the value of x, the first step is to calculate the measure of y.
Angle y:
This angle is supplementary to both external angles, 55º and 65º, this means that the three angles measure 180º:
From this expression, you can determine the value of y.
-Simplify the like terms and pass the result to the right side of the equation by applying the opposite operation to both sides of the equal sign:
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