SOLUTION: Please help me solve this {{{highlight(cross(question))}}} {{{highlight(problem)}}}. A boy is three times as old as his sister. In 7 years he will be twice as old as his sister w

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Question 1203980: Please help me solve this highlight%28cross%28question%29%29 highlight%28problem%29.
A boy is three times as old as his sister. In 7 years he will be twice as old as his sister will be,
find their present ages.
Found 2 solutions by Edwin McCravy, ikleyn:
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
Please help me solve this question. A boy is three times as old as his sister.
B+=+3%2AS
In 7 years he will be twice as old as his sister will be, find their present ages.
B%2B7+=+2%28S%2B7%29

system%28B=3%2AS%2CB%2B7=2%2A%28S%2B7%29%29

Simplify and solve the system by substitution.

Edwin

Answer by ikleyn(52754) About Me  (Show Source):
You can put this solution on YOUR website!
.
Please help me solve this question. A boy is three times as old as his
sister. In 7 years he will be twice as old as his sister will be, find
their present ages.
~~~~~~~~~~~~~~~~~~~~~~ 

Let x be the sister's age (in years).

Then the brother's age is 3x years, according to the problem.


In 7 years

    the sister      the brother
      2(x+7)      =   3x+7.


Simplify and find x

    2x + 14 = 3x + 7

    14 - 7 = 3x - 2x

      x   =    7.


Thus, the sister's current age  is 7 years; the brother's current age is 3*7 = 21 years.

Solved.


====================

A post-solution note

            (1)   when a male is  21  year old,  the word  " a boy "  is just not appropriate.


            (2)   " solve the question "   is the mafia's vocabulary.

                    Normal people say  " solve the problem ".   Or  " answer the question ".