SOLUTION: Frank is eight years older than his sister, Amy. In three years he will be twice as old as she will be. how old are they right know?

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Question 1172287: Frank is eight years older than his sister, Amy. In three years he
will be twice as old as she will be. how old are they right know?

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Frank, x+8
His sister, x

%28x%2B8%29%2B3=2%28x%2B8%29---------find his sister's age.

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.

Let x be the sister current age.

Then  Frank is (x+8) years old.



In 3 years,  the sister age will be (x+3) years,

while Frank will be (x(x+8) + 3) = (x+11) years old.



The condition says that

    x+11 = 2*(x+3).


Simplify and solve

    x + 11 = 2x + 6

    11 - 6 = 2x - x

       5   = x


ANSWER.  The sister is 5 years old.  Frank is 5+8 = 13 years old.

Solved.


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The setup equation in the post by @josgarithmetic   highlight%28%28x%2B8%29%2B3=2%28x%2B8%29%29   is  TOTALLY  WRONG   highlight%28cross%28%28x%2B8%29%2B3=2%28x%2B8%29%29%29
and leads to  INCORRECT  NON-SENSICAL  answer  x= -5.

For your safety,  IGNORE  that post.