Answer:
15
Step-by-step explanation:
You want the length of segment CD of segment BD, given BC=x+4, CD=5x, and BD=5x+7.
Segment addition
A whole segment is the sum of its parts:
BD = BC +CD
5x +7 = (x +4) +(5x)
3 = x . . . . . . . . . . . . . subtract 5x+4 from boths sides
The length CD is then ...
CD = 5x = 5(3)
CD = 15
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Additional comment
BC = 3+4 = 7; BD = 5(3) +7 = 22.
