Answer: 15 cm
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Work Shown:
AC/DF = BC/EF ... see note below
9/x = 15/25
9*25 = x*15 ... cross multiply
225 = 15x
15x = 225
15x/15 = 225/15 ... divide both sides by 15
x = 15
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note: AC and DF are the sides that go downhill as you read from left to right, so they pair up. The sides BC and EF climb uphill as we read from left to right, so they pair up as well. We divide in the same order (green to blue) to keep the proportions the same.
