1) find the supplement of the 113 degree angle; it is 180-113, or 67, degrees.
2) recognizing that the sum of the interior angles of a triangle is 180 degrees, add up 67 and 72 degrees, obtaining 139 degrees, and subtract this sum from 180 degrees:
180 degrees - 139 degrees = 41 degrees (answer)
The steps are outlined above; the end result is that <B is 41 degrees.
