We have the following:
Since we consider that both triangles are similar, we have that AB measures the same as DE, therefore we can equate it
[tex]\begin{gathered} AB=DE \\ 3x+6=4x \end{gathered}[/tex]
solving for x
[tex]\begin{gathered} 4x-3x=6 \\ x=6 \end{gathered}[/tex]
Therefore AB:
[tex]AB=3\cdot6+6=24[/tex]
The length of AB is 24
