We are given a figure with a triangle with two known angles and one unknown angle. That unknown angle further extends to form a straight line and we are to find that exterior angle z.
We know that the sum of all three angles of a triangle is 180°. So the third unknown angle of the given triangle will be = 180 - (45 + 72) = 63°.
We also know that angles on one side of a straight line always add to 180°.
