Question

find the measure of 13 years ago

Answer 1

120. 180-60

Answer 2

Since AB is a straight line, sum of adjacent angles on that line will equal 180.

so <CEB + <CEA = 180.

60 + <CEA = 180.

Hence <CEA = 60.

(You can also call both angles as allied angles or angles in a linear pair.)

Answer 3

oops <CEA = 120 :P but the concept is same