The length of CD will be option C. 3
From given diagram, triangle ABC and EDC meet at a common vertex C.
So, triangle ABC and EDC both are congruent to each other.
Applying the similarity property of congruence, ratio of the congruent triangles' corresponding sides will be equal.
Therefore,
AB/ED = AC/EC = BC/CD
AC/EC = BC/CD
18/6 = (12 - x)/x
Simplifying the expression,
We get
18x = 6(12 - x)
Multiplicating the terms in right hand side,
18x = 72 - 6x
Solving 6x on both sides,
we get
18x + 6x = 72 - 6x + 6x
24x = 72
Dividing both the sides by 24, we get
24x/24 = 72/24
x = 3
Hence, the length of CD is 3.
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