Hello from MrBillDoesMath!
Answer:
36 degrees
Discussion:
The attachment shows calculated angles in red. As a straight line has 180 degrees the missing angle at A is 180 - 72 = 108 degrees (shown in red). The missing angle at B is 180 - 144 = 36. As a triangle has 180 degrees.
x + 108 + 36 = 180 => as 180 + 36 = 144
x + 144 = 180 => subtract 144 form both sides
x = 180 - 144 = 36
Thank you,
MrB
