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Find the measure of each marked angle. Assume the lines are parallel.

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Find the measure of each marked angle. Assume the lines are parallel.

Two parallel lines that rise from left to right intersect a horizontal line, each forming four angles. Where the line on the left intersects the horizontal line, the top right angle measures (x plus 1) degrees.

Where the line on the right intersects the horizontal line, the top left angle measures (9x minus 21) degrees.

left parenthesis x plus 1 right parenthesis degrees(x+1)°

left parenthesis 9 x minus 21 right parenthesis degrees(9x−21)°

x+1= ____°

9x−21= ___°

#1
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These angles are supplementary, so...

(x + 1)°  +  (9x - 21)°   =   180°

x + 1 + 9x - 21   =   180

Combine  x  and  9x  to get  10x , and combine  1  and  -21  to get  -20 .

10x - 20  =  180

Add  20  to both sides of the equation.

10x   =   200

Divide both sides of the equation by  10 .

x   =   20

So....

x + 1   =   20 + 1   =   21

9x - 21   =  9(20) - 21   =   159

hectictar  Dec 1, 2017
Sort:

#1
+5555
+2

These angles are supplementary, so...

(x + 1)°  +  (9x - 21)°   =   180°

x + 1 + 9x - 21   =   180

Combine  x  and  9x  to get  10x , and combine  1  and  -21  to get  -20 .

10x - 20  =  180

Add  20  to both sides of the equation.

10x   =   200

Divide both sides of the equation by  10 .

x   =   20

So....

x + 1   =   20 + 1   =   21

9x - 21   =  9(20) - 21   =   159

hectictar  Dec 1, 2017

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