Answer:
x = 19
Explanation:
The 3 angles are supplementary and sum to 180°
Sum the 3 angles and equate to 180
5x + 4 + x - 2 + 3x + 7 = 180 , that is
9x + 9 = 180 ( subtract 9 from both sides )
9x = 171 ( divide both sides by 9 )
5x+4+x-2+3x+7=9x+9=180,x+1=20,x=19
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