Question 1118415
{{{A/M=5/3}}}


{{{A+7=3(M-7)}}}


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{{{system(3A=5M,A+7=3M-21)}}}


{{{system(3A-5M=0,A-3M=-28)}}}


{{{system(5M-3A=0,3M-A=28)}}}


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{{{A=3M-28}}}
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{{{5M-3(3M-28)=0}}}

{{{5M-9M+84=0}}}

{{{-4M=-84}}}

{{{highlight(M=21)}}}