Answer:
The length of DC is 3 unit.
Step-by-step explanation:
Consider the provided figure.
DE is parallel to CB.
According to basic proportionality theorem:
"If a line is drawn parallel to one side of a triangle to pass the other two sides in separate points, the other two sides are divided into the same ratio."
Therefore
[tex]\frac{AE}{EB}=\frac{AD}{DC}[/tex]
[tex]\frac{12}{4}=\frac{9}{x}[/tex]
[tex]3=\frac{9}{x}[/tex]
[tex]x=\frac{9}{3}[/tex]
[tex]x=3[/tex]
Thus, the length of DC is 3 unit.
