If two angles are supplementary, they must

add up to
add up to
be adjacent
be congruent

If two angles are supplementary, their sum is 180º and they can be expressed as x and 180-x. If they are congruent ,then the two angles are equal: 
x=180-x 
2x=180 
x=90º and 180-x=90º 
 The 2 angles have to add to 180 degrees

It creates dogx^2 and then flip your answer and multiply by 2

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