Question 318601
Let A be Joe's age now, B Jim's age now.
1.{{{A+B=28}}}
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In 7 years, Joe will be {{{A+7}}}, Jim will be {{{B+7}}}
{{{A+7=2(B+7)}}}
{{{A+7=2B+14}}}}
2.{{{A-2B=7}}}
Subtract eq. 1 from eq. 2,
{{{A-2B-A-B=7-28}}}
{{{-3B=-21}}}
{{{highlight( B=7)}}}
Then from eq. 1,
{{{A+7=28}}}
{{{highlight( A=21)}}}
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Jim is now 21 and Joe is now 7.