From the figure, find x.

65 70 75 45

70

In ΔACO, ∠ACO + ∠CAO + ∠AOC = 180o = 45o + 90o + ∠AOC = 180o ∠AOC = 45o ∠AOC = ∠DOB = 45o ( vertically opposite angles ) In ΔDOB, ∠DOB + ∠DBO + ∠OBD = 180o = 45o + xo + 65o = 180o x = 70o