
1) build LM || WV ( therefore ∠ LME=90)
2) suppose ∠XNE=α⇒∠XEN=∠LEM=(90−∠XNE)=90−α (from the triangle XEN)
3) From the triangle LME:
∠MLE=(90−∠MEL)=90−(90−α)=α
4) From the triangles XEN and LME:
cos(α)=XN/EN=LE/LM
5) LM = WV (because WLMV – is a rectangle)
6) XN/EN = LE/WV ⇒ XN = EN * (LE/WV) = 18 * (6/9) = 12
Answer: XN=12