X^2+y^2=74 x+y=12 Решите систему, если можно поподробнее. Спасибо.

Решите задачу:

$\left \{ {{x^2+y^2=74} \atop {x+y=12}} \right. \left \{ {{x^2+y^2=74} \atop {x=12-y}} \right. \left \{ {{(12-y)^2+y^2=74} \atop {x=12-y}} \right. \left \{ {{144-24y+y^2+y^2=74} \atop {x=12-y}} \right.\\ \left \{ {{2y^2-24y+70=0} \atop {x=12-y}} \right. \left \{ {{2(y^2-12y+35)=0} \atop {x=12-y}} \right. \left \{ {{2(y-5)(y-7)=0} \atop {x=12-y}} \right.\\ y_{1}= 5;y_{2}= 7;\\ x_{1}= 12-5=7; x_{1}= 12-7=5;$