As #bar(AC)# is the perpendicular bisector of #bar(BD)#, we have #BC = CD#.
As #AB# and #AD# are both hypotenuses of right triangles with legs of length #BC# and #AC# (#triangle ACB# and #triangle ACD#, respectively), we know that #AB = AD#. Equating the two, we get
#AB = AD#
#=> 2x-14 = 37-x#
#=> 3x = 51#
#=> x = 17#