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}} ight. left { {{x=7-y} atop {5(7-y)-3y=11}} ight. left { {{x=7-y} atop {y=3}} ight. left { {{x=4} atop {y=3}} ight. [/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}} ight. left { {{y=2x-3} atop {y=3x-5}} ight. left { {{3x-5=2x-3} atop {y=3x-5}} ight. left { {{x=8} atop {y=19}} ight. [/latex][latex]3x-5=2x-3[/latex][latex]x=8[/latex]