А) ( x + y = -5
( 3x - y = -7
( x = -5 - y
( 3*(-5 - y) - y = -7
-15 - 3y = -7
-3y = -7 + 15
-3y = 8
y = -8/3
y = -2 2/3
x = -5 - 2 2/3 = -7 2/3
Ответ: (-7 2/3; -2 2/3)
б) x - 2y = 7
3x + 2y = 5
x = 7 + 2y
3*(7 + 2y) + 2y = 5
21 + 6y + 2y = 5
8y = 5 - 21
8y = -16
y = -2
x = 7 + 2*(-2) = 7 - 4 = 3
Ответ: (3; -2)