[tex]3x+4y=12 \ \ |\ subtract\ 3x\ to\ both\ sides \\\\ 4y=-3x+12 \ \ | \ divide \ both \ sides\ by\ 4\\\\ y=-\frac{3}{4}x+3\\\\x=-4 \ \ \to \ \ y= -\frac{3}{4}x+3=-\frac{3}{4} \cdot (-4)+3=3+3=6\\\\x=8 \ \ \to \ \ y= -\frac{3}{4}x+3=-\frac{3}{4} \cdot8+3=-6+3=-3[/tex]
