Найдите у-3х,если х-0,5у=7,а 2х+4у=-16

Х - 0,5y = 7 ==> 0,5y = x - 7 ==> y = 2x - 14
2x + 4y = - 16 ==> 4y = - 2x - 16 ==> y = - 0,5x - 4
2x - 14 = - 0,5x - 4
2,5x = 10
x = 4
y = - 0,5•4 - 4 = - 2
y - 3x = - 2 -3•4 = -14
ответ ( - 14 )