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

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