`12x3y` `\vdots` `45` → `12x3y` `\vdots` `5` `,` `\vdots` `9`
Để `12x3y` `\vdots` `5` → \(\left[ \begin{array}{l}y=0\\y=5\end{array} \right.\)
Thay `y=5`
→ `12x35` `\vdots` `9`
→ `1+2+x+3+5` `\vdots` `9`
→ `11+x` `\vdots` `9`
→ `x=7`
Thay `y=0`
→ `12x30` `\vdots` `9`
→ `1+2+x+3+0` `\vdots` `9`
→ `6+x` `\vdots` `9`
→ `x=3`
Vậy
\(\left[ \begin{array}{l}x=3\\y=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=7\\y=5\end{array} \right.\)
