Question 1007819


{{{r + 2s - t =4}}}
{{{2r + 2s -6t =12}}}
{{{-2r - 2s -2t =4}}}
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*[invoke cramers_rule_3x3 1, 2, -1, 4, 2, 2, -6, 12, -2, -2, -2, 4]

note, your 
{{{r}}}={{{x}}}
{{{s}}}={{{y}}}
{{{t}}}={{{z}}}

so, solutions are 
{{{r= -2}}}, 
{{{s=2}}}, and 
{{{t= -2 }}} 
giving the ordered triple 
({{{-2}}}, {{{2}}}, {{{-2}}})