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put this solution on YOUR website!Mark is 11 years older that his sister. In 8 years he will be twice as old as she will be then. How old are they now?
Here's what I have so far: m=s+11+2s+8.
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Let x = age of sister
then because "Mark is 11 years older that his sister."
x+11 = age of Mark
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From: "In 8 years he will be twice as old as she will be then."
we get our equation of:
(x+11) + 8 = 2(x+8)
x + 11 + 8 = 2x + 16
x + 19 = 2x + 16
x + 3 = 2x
3 years = x (Mark's sister's age)
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Mark's age:
x+11 = 3+11 = 14 years (Mark's age)
