Ответ:

Объяснение:

[tex]1)\left \{ {{x=3y-7} \atop {2x+9y=13}} \right. \\\\\left \{ {{x=3y-7} \atop {2(3y-7)+9y=13}} \right. \\\\2(3y-7)+9y=13\\6y-14+9y=13\\15y=27\\y=\frac{27}{15}[/tex]