Answer:
(d) 6.3
Explanation:
You want the measure of side CD in ∆CDE ~ ∆CFG with CG=6, GE=2.4, and FD=1.8.
Proportion
The corresponding sides of the two triangles are proportional:
CD/CE = FD/GE
CD = CE×FD/GE = (6+2.4)×1.8/2.4
CD = 6.3
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Additional comment
Lengths on segment CD are 3/4 of those on segment CE, so CF = 4.5. CD is the sum of CF and FD: 4.5 +1.8 = 6.3.