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1. Ana's father is 5 times older than Ana and Ana is twice as old than his sister Alice. In two years time, the sum of their ages will be 58. How old is Ana now?
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One way to assign the variables is this:
Ana n
Father 5n+n=6n
Alice n/2
Another way, is to let Alice's age be the main variable:
Ana 2c
Father 5*2c+2c=12c
Alice c
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In two years time, the sum of their ages will be 58.
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----------In this case, maybe recheck the work, OR recheck your original problem statement very carefully.