Rozwiąż układ równań dla y=1/3x+3 i y+x=7

Rozwiązanie zadanego układu równań metodą podstawiania:

$\begin{cases} y-\frac{x}{3}=3 \\  y+x=7 \end{cases}$

$x+3y=9x+y=7 $
$ $
$ $
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$varctx=c.getContext("2d"); $
$ctx.font="18pxArial"; $
$ctx.strokeStyle="#202020";ctx.strokeStyle="#b22222";ctx.strokeText("x",7,24);ctx.font="12pxArial"; $
$ctx.moveTo(27,24);ctx.lineTo(291,24);ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("7",7,48);ctx.moveTo(27,48);ctx.lineTo(291,48);ctx.stroke(); $
$ctx.strokeText("6",7,72);ctx.moveTo(27,72);ctx.lineTo(291,72);ctx.stroke(); $
$ctx.strokeText("5",7,96);ctx.moveTo(27,96);ctx.lineTo(291,96);ctx.stroke(); $
$ctx.strokeText("4",7,120);ctx.moveTo(27,120);ctx.lineTo(291,120);ctx.stroke(); $
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$ctx.strokeText("1",7,192);ctx.moveTo(27,192);ctx.lineTo(291,192);ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("0",7,216);ctx.moveTo(27,216);ctx.lineTo(291,216);ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-1",7,240);ctx.moveTo(27,240);ctx.lineTo(291,240);ctx.stroke(); $
$ctx.strokeText("-2",7,264);ctx.moveTo(27,264);ctx.lineTo(291,264);ctx.stroke(); $
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$ctx.strokeStyle="#202020";ctx.strokeStyle="#b22222";ctx.font="18pxArial"; $
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i: Ostateczne rozwiązanie to:

x = -y + 7

  3y - (-y +7) = 9
  4y = 16
  4y = 16 

  y = 4 
  y = 4
  x = -y+7  x = -(4)+7 = 3 
 {y,x} = {4,3}