Angle ABD=58 which makes angle ABC = 88 and angle ACB =44. AC/AD=sin(x+16)/sin(x) =AC/AB=sin(88)/sin(44) which leads us to a simple equation like: sin(x+16)/sin(x) = 2cos(44) which gives x=30 deg since sin(46)=cos(44). Thus, x=30 deg.
I still would like to know how this done by plane geometry alone.