Question

$\left \{ {{3x-4y=18} \atop {5x+2=4}} \right.$
x+y-?

Answer 1

3x - 4y = 18
5x + 2y = 4

x = 6 + 4/3y
30 + 20/3y + 2y = 4

x = 6 + 4/3y
26/3y = -26

x = 6 + 4/3 * (-3)
y = -3

x = 2
y = -3

2-3= -1
Ответ: -1