Rozwiąż układ równań dla 7x-10=3y i y-3=4x

Rozwiązanie zadanego układu równań metodą podstawiania:

$\begin{cases}7x-10=3y \\ y-3=4x \end{cases}$

$-3y+7x=10y-4x=3 $
$ $
$ $
$varc=document.getElementById("myCanvas"); $
$varctx=c.getContext("2d"); $
$ctx.font="18pxArial"; $
$ctx.strokeStyle="#202020";ctx.strokeStyle="#b22222";ctx.strokeText("y",7,24);ctx.font="12pxArial"; $
$ctx.moveTo(27,24);ctx.lineTo(291,24);ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-8",7,48);ctx.moveTo(27,48);ctx.lineTo(291,48);ctx.stroke(); $
$ctx.strokeText("-9",7,72);ctx.moveTo(27,72);ctx.lineTo(291,72);ctx.stroke(); $
$ctx.strokeText("-10",7,96);ctx.moveTo(27,96);ctx.lineTo(291,96);ctx.stroke(); $
$ctx.strokeText("-11",7,120);ctx.moveTo(27,120);ctx.lineTo(291,120);ctx.stroke(); $
$ctx.strokeText("-12",7,144);ctx.moveTo(27,144);ctx.lineTo(291,144);ctx.stroke(); $
$ctx.strokeText("-13",7,168);ctx.moveTo(27,168);ctx.lineTo(291,168);ctx.stroke(); $
$ctx.strokeText("-14",7,192);ctx.moveTo(27,192);ctx.lineTo(291,192);ctx.stroke(); $
$ctx.strokeText("-15",7,216);ctx.moveTo(27,216);ctx.lineTo(291,216);ctx.stroke(); $
$ctx.strokeText("-16",7,240);ctx.moveTo(27,240);ctx.lineTo(291,240);ctx.stroke(); $
$ctx.strokeText("-17",7,264);ctx.moveTo(27,264);ctx.lineTo(291,264);ctx.stroke(); $
$ctx.strokeText("-18",7,288);ctx.moveTo(27,288);ctx.lineTo(291,288);ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-9",19,310);ctx.moveTo(27,0);ctx.lineTo(27,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-8",43,310);ctx.moveTo(51,0);ctx.lineTo(51,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-7",67,310);ctx.moveTo(75,0);ctx.lineTo(75,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-6",91,310);ctx.moveTo(99,0);ctx.lineTo(99,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-5",115,310);ctx.moveTo(123,0);ctx.lineTo(123,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-4",139,310);ctx.moveTo(147,0);ctx.lineTo(147,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-3",163,310);ctx.moveTo(171,0);ctx.lineTo(171,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-2",187,310);ctx.moveTo(195,0);ctx.lineTo(195,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("-1",211,310);ctx.moveTo(219,0);ctx.lineTo(219,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeText("0",235,310);ctx.moveTo(243,0);ctx.lineTo(243,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.strokeStyle="#202020";ctx.strokeStyle="#b22222";ctx.font="18pxArial"; $
$ctx.strokeText("x",259,310);ctx.font="11pxArial"; $
$ctx.moveTo(267,0);ctx.lineTo(267,290);ctx.strokeStyle='#eee9e9';ctx.stroke(); $
$ctx.beginPath();ctx.moveTo(214,0);ctx.lineTo(91,288);ctx.lineWidth=3;ctx.strokeStyle="#ff3399";ctx.stroke(); $
$ctx.beginPath();ctx.moveTo(187,0);ctx.lineTo(116,288);ctx.lineWidth=3;ctx.strokeStyle="#006633";ctx.stroke(); $

i: Ostateczne rozwiązanie to:

y = 4x + 3

  7x - 3•(4x+3) = 10
  -5x = 19
  5x = - 19 

  x = - 19/5 
  x = -19/5
  y = 4x+3  y = 4(-19/5)+3 = -61/5 
 {x,y} = {-19/5,-61/5}