How do i find the largest angle of the triangle ? ?

89

43 + x = 132 => Exterior Angle Theorem
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The measure of an exterior angle of a triangle is greater than either of the measures of the remote interior angles. That means the two remote interior angle add up to the exterior angle.

x = 89

**To find the last angle: 89 + 43 + x = 180 => Triangle Sum Theorem states that the interior angles of a triangle add up to 180. The last angle would be 48.**

12+3b -1=-5-b -12-1+5=-b-3b -8=-4b