We know that
To prove that AC=FH, we need to use the sum of segments property.
According to the given graph, segment AC is formed by
Similarly, FH is defined
But, we know by given that AB=GH and BC=FG, that means we can replace this on either equation
Using the commutative property, we have
And we know that FH=FG+GH, so
Therefore, AB=FH.