Question

696 и 697 вторые столбики

Answer 1

696 в) $\left \{ {{7x-y=0} \atop {3x-y+12=0}} \right. \left \{ {{y=7x} \atop {3x-7x-12}} \left \{ {{y=7x} \atop {-4x+12=0}} \right. }} \right. \left \{ {{y=7x} \atop {-4x=-12}} \right. \left \{ {y=7x} \atop {x=3}} \right. \left \{ {{y=21} \atop {x=3}} \right.$