I got the 6 inches. The part I was stuck on was that I did not see that the distance from A.1 to B is the same distance from the first "X" on your diagram to A.
Is there is concept I am missing?
see, the question states that we have 4 identical figures. thus, the left half of the figure has 2 identical figures. consider this as a trapezium. except the angled part, two opposite sides are equal i.e. the smaller side of the trapezium is equal to longer side + side under angled part.
you know the angled one is 6 incehes. the remaining (remember, identical figure) part will be: whole length - 6 inches.
is that clear?? I still have hangover