Answer: 
Step-by-step explanation:
Since C is a point in BD, we add BC and CD, then set it equal to BD.
11+x+9=4x+4 [combine like terms]
20+x=4x+4 [subtract both sides by x]
20=3x+4 [subtract both sides by 4]
16=3x [divide both sides by 3]
x=16/3
Now that we have x, we plug it into BD to find the length.
BD=4(16/3)+4 [multiply]
BD=64/3+4 [rewrite 4 into fraction]
BD=64/3+12/3 [add]
BD=76/3
Since this is not a proper fraction, we can write it as a mixed number.
