{4x-y=5
{3x+2y=12;
{y=-5+4x
3x+2(-5+4x)=12;
x=2;
y=-5+4×2;
y=3;
(x,y)=(2,3);
{4×2-3=5
{3×2+2×3=12;
{5=5
{12=12;
(x,y)=(2,3).
{4x-y=5
{3x+2y=12;
{y=-5+4x
{3x+2y=12;
3x+2(-5+4x)=12;
x=2;
y=-5+4×2;
y=3;
(x,y)=(2,3);
{4×2-3=5
{3×2+2×3=12;
{5=5
{12=12;
(x,y)=(2,3).