Question

$left { {{7x+9y=8} atop {9x-8y-69}} right.$

Answer 1

7х+9у=8      I 8
9х-8у=69    I 9
56х+72у=64
81х-72у=621
сложим
137х=685
х=5
у=(8-7х)/9=-27/9=-3