Answer: Choice D
x = 5, AB = 14, BC = 8
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Explanation:
The triangles are similar, which can be proven through the angle angle theorem.
The similar triangles allow us to form the proportion below.
EB/DB = AB/BC
7/4 = (2x+4)/(x+3)
7(x+3) = 4(2x+4)
7x+21 = 8x+16
21-16 = 8x-7x
5 = x
x = 5 is part of the answer
Then we can use that x value to find the following
AB = 2x+4 = 2*5+4 = 14 is the length of AB
BC = x+3 = 5+3 = 8 is the length of BC
