Answer:
6
Step-by-step explanation:
You have to separate the triangles into two, where you can compare short over long. DC = AB, so DC is the long side in the smaller triangle and AC is the shorter side. DC is similar to AC, and DE is similar to AB. Short over long side formula gives you [tex]\frac{x}{9} =\frac{4}{x}[/tex].
Cross multiply to get [tex]x^2=36[/tex]
Square root on both sides to get [tex]x=6[/tex]
