4x - 7y = 3 x - 7y = 15
\(\left \{ {{4x-7y=3} \atop {x-7y=15}} \right. \\\\ \left \{ {{4x-7y=3} \atop {x=15+7y}} \right. \\\\ substitution\ method\\\\ 4*(15+7y)-7y=3\\\\ 60+28y-7y=3\\\\ 60+21y=3\ \ \ \ | subtract\ \\\\ 21y=-57\\\\ y=-\frac{57}{21}=-\frac{19}{7}\\\\ x=15+7*(-\frac{19}{7})=15-19=-4\\\\\ Solution :\ \left \{ {{y=-\frac{19}{7}} \atop {x=-4}} \right.\)
