Supplementary angles are when two angles have a sum of 180°.180°. Typically, these angles lie on a straight line.
The sum of the interior angles in a triangle is 180°180°
To solve for bb, solve for its supplementary angle by adding the given interior angles and setting their sum to 180°180°
Let this supplementary angle be aa.
First, we can see from the diagram that the exterior angle 125°125° and the interior angle aa lie on a straight line. Therefore, they are supplementary angles
Since supplementary angles add to 180°,180°, add the angle measures and set their sum to 180°.180°. Then, solve for the value of aa.
a+125a+125
==
180180
a+125a+125-125−125
==
180180-125−125
Subtract 125125 from both sides
aa
==
55°55°
Finally, since the interior angles of a triangle add to 180°,180°, add the angle measures and set their sum to 180°.180°. Then, solve for bb.
