Решите системe уравнения а)x+y=7 5x-3y=11

[latex]\begin{cases}x+y=7|*3\\5x-3y=11\end{cases}<=>\begin{cases}3x+3y=21\\+\\5x-3y=11\end{cases}\\\\.\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8x=32\\.\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x=4\\x+y=7=>y=7-x=3\\OTBET:(4;3)[/latex]