Question 703058

let Mary's age be {{{x}}} and her son's age {{{y}}}

given:


Mary is three times as old as her son: {{{x=3y}}}.......eq.1


in {{{12}}} years, Mary's age will be {{{one}}} year {{{less}}} than {{{twice}}} her sons age:

{{{x+12=2(y+12)-1}}}.......eq. 2

solve this system:

{{{x=3y}}}.......eq.1
{{{x+12=2(y+12)-1}}}.......eq. 2
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{{{x+12=2(y+12)-1}}}.......eq. 2...substitute {{{x}}} from eq. 1

{{{3y+12=2(y+12)-1}}}

{{{3y+12=2y+24-1}}}

{{{3y-2y=24-12-1}}}

{{{y=11}}}.......son's age

and

{{{x=3y}}}
{{{x=3*11}}}
{{{x=33}}}.......Mary's age