Find angle ACB in terms of x using tangent

Question

Angle ABC = x
Line BC is tangent to circle centre O
Line AOC is a straight line
Find angle ACB in terms of x

I got 270-2x:
Angle OAB = OBA = x-90
Angle ACB= 180-(x-90)-x
Apperently this is the wrong answer but I can't wrap my head around why.

Thanks


 

Answer 1

I arrived at the same answer: 270-2x taking a longer route to get there than you, but still the same answer. Strange.