Question 1140938
{{{system(3x+y=9,9x+3y=12)}}}


At least simplify the second equation, division by 3 both sides:


{{{system(3x+y=9,3x+y=4)}}}
Next, regardless of substitution or elimination method, these are two parallel lines so NO SOLUTION for the system.


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Look!  Simplifying the second equation gives you two equations representing lines <b>WITH THE SAME SLOPE</b>.  The lines will be parallel and <b>do NOT intersect</b>.

<b>NO SOLUTION!</b>



Still not satisfied?  Try substitution.  Take first equation and solve for y in terms of x.
{{{y=-3x+9}}}
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The second equation of the system was already simplifiable to {{{3x+y=4}}}.  Now substitute for y:
{{{3x+(-3x+9)=4}}}
{{{3x-3x+9=4}}}
{{{9=4}}}
Do you see a contradiction here?   Did you find a solution for the variable, x?  
NO SOLUTION