Умножим первое уравнение на 16, второе на 6:
15x + 7y – 4(3x – y) = –16 => 15x + 7y – 12x + 4y = –16 => 3x + 11y = –16.
18x – (10 – y) = 12(2 – y) => 18x – 10 + y = 24 – 12y => 18x + 13y = 34.
Умножим первое уравнение на 6: 18x + 66y = –96.
Вычтем из второго: (18x + 13y) – (18x + 66y) = 34 – (–96) => –53y = 130 => y = –130/53.
3x = –16 – 11y = –16 – 11(–130/53) = –16 + 1430/53 = (–848 + 1430)/53 = 582/53.
x = 582/(53 * 3) = 194/53.
Ответ: x = 194/53, y = –130/53.