Answer:
9
Step-by-step explanation:
ED: DC = 3:1
AB : BC = 3:1
AB: 3 = 9
AB = 9
Tale's theorem
[tex]\frac{12}{4} =\frac{AB}{3}[/tex]
[tex]AB=\frac{(12)(3)}{4} =\frac{36}{4} =9[/tex]
Hope this helps