Respuesta :

by the Angle sum property of triangle,

55+75+(-6+7x) = 180

=> 130 +(-6+7x) = 180

=> (-6+7x) = 180-130

=> (-6+7x) = 50

=> 7x = 50+6

=> 7x = 56

=> x= 56/7

=> x = 8

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