This question is not difficult, is it?
AC-AC-DC extension line parallel to point e when crossing point b, CE=AB because AB is parallel to CE.
So DE= 13 (AB+CE= 13 can be deduced from the neutral line).
Then you can see the right triangle with 5 12 13 pythagorean number in the triangle BDE, and then you can calculate the height of the trapezoid.
Then set the unknown number, AB as x, CD as 13-x, and simplify algebra according to similar triangles.