Question

5x +6 y=13
7x+18y+1=0
решите методом постоеовки плдииииииззззззззззззз

Answer 1

$left { {{5x +6 y=13} atop {7x+18y+1=0 }} right.$

$left { {{y=(13 - 5x)/6} atop {7x+18y+1=0 }} right.$
7x+18y+1=0 
7x+18(13 - 5x)/6+1=0 
7x + 3(13 - 5x) + 1 = 0
7x + 39 - 15x +1 = 0
40 = 15x - 7x
40 = 8x
x = 5
y=(13 - 5x)/6
y=(13 - 25)/6
y = - 12/6
y = -2