1/х -20у + 15z = 18, 1/y -15z + 18x = 20, 1/z -18x + 20y = 15 решите систему х,z и у...

$x-20y+15z=\frac{1}{18} \\ y-15z+ x-y = \frac{1}{180} \\ 3y-2z = \frac{1}{60} \\$
Сложив уравнения попарно
$x-20y+15z=\frac{1}{18} \\ y-15z+x-y = \frac{1}{180} \\ 3y-2z = \frac{1}{60} \\ 16z-17x = \frac{11}{90} \\ \\ 3y-2z=\frac{1}{60} \\ 16z-17*(\frac{1}{180}+y) = \frac{11}{90} \\$
$x = \frac{1}{18}\\ y = \frac{1}{20} \\ z = \frac{1}{18}$