Решите системы уравнений : а)х+у=7 б) 2х-у=3 5х-3у=11 3х-у=5

[latex]\left \{ {{x+y=7} \atop {5x-3y=11}} \right. \left \{ {{x=7-y} \atop {5(7-y)-3y=11}} \right. \left \{ {{x=7-y} \atop {y=3}} \right. \left \{ {{x=4} \atop {y=3}} \right. [/latex] [latex]5(7-y)-3y=11[/latex] [latex]35-5y-3y=11[/latex] [latex]8y=24[/latex] [latex]y=3[/latex] [latex] \left \{ {{2x-y=3} \atop {3x-y=5}} \right. \left \{ {{y=2x-3} \atop {y=3x-5}} \right. \left \{ {{3x-5=2x-3} \atop {y=3x-5}} \right. \left \{ {{x=8} \atop {y=19}} \right. [/latex] [latex]3x-5=2x-3[/latex] [latex]x=8[/latex]