The lines AB AB\,AB and CD CD\,CD are parallel. Point F F\,F lies on the line ABABAB. A transversal line connects point F F\,F to point E E\,E on the line CDCDCD, such that ∠CEF=115∘\angle CEF = 115^\circ∠CEF=115∘. A triangle EFG EFG\,EFG is constructed where ∠FEG=42∘\angle FEG = 42^\circ∠FEG=42∘ and ∠FGE=72∘\angle FGE = 72^\circ∠FGE=72∘.
Find the size of angle xxx, where x=∠GFBx = \angle GFBx=∠GFB.
Give a reason for each stage of your working.