Фигурная скобка х+2у=5 -х+7у=13

[latex] left { {{x=5-2y} atop {-(5-2y)+7y=13}} ight. [/latex][latex] left { {{x=5-2y} atop {-5+2y+7y=13}} ight. [/latex][latex] left { {{x=5-2y} atop {9y=18}} ight. [/latex][latex] left { {{x=5-2*2} atop {y=2}} ight. [/latex][latex] left { {{x=1} atop {y=2}} ight. [/latex]