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

[tex] \left \{ {{5x +6 y=13} \atop {7x+18y+1=0 }} \right. [/tex]

[tex] \left \{ {{y=(13 - 5x)/6} \atop {7x+18y+1=0 }} \right. [/tex]
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