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.