Answer:

Step-by-step explanation:
Given



Required
Determine CD
Since, C is a point on BD, the relationship between the given parameters is;

Substitute the values of BD, BC and CD

Collect Like Terms


Divide both sides by -4


To determine the length of CD;
Substitute 3 for x in 
Hence;

Answer:
13
Step-by-step explanation:
4+(-3)-2*(-6)
4-3-2*-6
1-(-12)
1+12
13
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I think the answer is 123