Question 173616
.
Let x = Amy's age
then from "Claire, who is six years older then her sister Amy"
x+6 = Claire's age
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From:"<Claire> is now three times as old as Amy was four years ago."
x+6 = 3(x-4)
x+6 = 3x-12
6 = 2x-12
18 = 2x
9 years = x (Amy's age)
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Claire's age:
x+6 = 9+6 = 15 years