We know, the measure of an arc is double the opposite inscribed angle.
so, 5x+25 = 2(4x-5.5)
or, 5x+25 = 8x-11
or, 25+11 = 8x-5x
or, 36 = 3x
or, 36/3 = x
or, 12 = x
so, x = 12
AC = 5x+25
= 5x12+25
= 60+25
= 85
