Hello from MrBillDoesMath!
Answer:
75
Discussion:
A plane triangle has 180 degrees. Using this in the diagram gives
x + 81 + angle BAC = 180 (***)
(The diagram is a bit fuzzy but I think the above numbers are accurate)
The diagram also shows that (156 + angle BAC )= 180 as a straight line has 180 degrees. So
angle BAC = 180 - 156 = 24
Substituting this in (***) above gives
x + 81 + 24 = 180 =>
x + 105 = 180 => (as 81 + 24 = 105)
x = 180 107 = 75
Check: Does
x + 81 + angle BAC = 180 ?
75 + 81 + 24 = 180. Yes
Thank you,
MrB