Question 1114949
{{{system(A+B+C=669,A-B-C=75,B-C=169)}}}
Three linear equations in three unknown variables.
Any solution method you want or need.


Notice what happens if you add corresponding members of the first two equations.  This quickly gives you the value of A.


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{{{(A+B+C)+(A-B-C)=669+75}}}
{{{2A=744}}}
{{{highlight(A=372)}}}


{{{system(B+C=297,B-C=169)}}}

{{{2B=466}}}

{{{highlight(B=233)}}}

{{{highlight(C=64)}}}