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Someone please help me out with this problem T-T I'm begging

Someone please help me out with this problem T-T I'm begging-example-1

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Label the vertices of the quadrilateral A, B, C, D. Angle C is supplementary to the angle of measure 60 degrees, so its own measure is 120 degrees.

AD and BC are parallel, as are AB and CD, so ABCD is a parallelogram. This means angle A also has measure 120 degrees. The angle adjacent to the one with measure
3x, part of angle A, then has measure
120^\circ-3x.

The three angles above the line through vertex A are supplementary, so we have


2x+90^\circ+(120^\circ-3x)=180^\circ


\implies210^\circ-x=180^\circ


\implies x=30^\circ

Someone please help me out with this problem T-T I'm begging-example-1
User Henk Straten
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