Question 1001791


{{{x=3}}}.....eq.1
{{{x+y=9}}}.....eq.2
{{{2x-y+2z=18}}}.....eq.3
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{{{x+y=9}}}.....eq.2..........substitute {{{3}}} for {{{x}}}

{{{3+y=9}}}

{{{y=9-3}}}

{{{y=6}}}


go to

{{{2x-y+2z=18}}}.....eq.3, substitute {{{3}}} for {{{x}}} and substitute {{{6}}} for {{{y}}}

{{{2*3-6+2z=18}}}

{{{6-6+2z=18}}}

{{{2z=18}}}

{{{z=18/2}}}

{{{z=9}}}