Alright, so for AB and CD to be parallel, CX and DX would have to be equal, as is with AX and BX. In addition, for CD and AB to be parallel, all sides in both triangles are either equal or not all sides in even one triangle are equal. Therefore, CD is not 3. In addition, two sides of a triangle combined must be greater than the third, so that leaves 5, 4, and 2 for CD. If it was 5, that would mean that all sides are equal, so that leaves 4 and 2. However, I don't see anything to prove either one right, sorry:/
