Question 973010
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Hi,

I have been trying to solve a word problem, here it is:

Three years ago, Evan was one third of his sister's age. In a year's time, Evan's age doubled will match his sister's age. How old is Evan now?

I know that I need to turn the problem into an equation and then solve, but I can not figure out how to turn the problem into an equation

Thanks
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Let Evan's age be E, and his sister's, S

"Three years ago, Evan was one third of his sister's age....." translates to: 
{{{E - 3 = (1/3)(S - 3)}}} ------ eq (i)
"In a year's time, Evan's age doubled will match his sister's age.....translates to: 2(E + 1) = S + 1 
                                                                                                                                             2E + 2 = S + 1     
                                                                                                                                       2E + 2 - 1 = S
                                                                                                                                             2E + 1 = S ------ eq (ii)

                    {{{E - 3 = (1/3)(S - 3)}}}
                    {{{E - 3 = (1/3)(2E + 1 - 3)}}} ---- Substituting 2E + 1 for S, in eq (i)
                    {{{E - 3 = (1/3)(2E - 2)}}}
                3E - 9 = 2E - 2 ----- Multiplying by LCD, 3
              3E - 2E = - 2 + 9
Evan's age, or E = 7</pre>