Hey there! :D
The midpoint and the outside line are symmetrical to eachother, 2(BF)= AE
Two midpoint segments equals one AE segment.
So, use the representation above and plug in the numbers.
2(23)= 5x -4
56= 5x-4
Add 4 to both sides.
60=5x
Divide by the 5.
x=12
I hope this helps!
~kaikers <3