3х-у=17,
2х+3у=-7;
-у=17-3х,
у=-17+3х,
2х+3(-17+3х)=-7;
2х-51+9х=-7;
2х+9х=-7+51;
11х=44;
х=4,
у=-17+12;
у=-5.
3х-у=17,
2х+3у=-7;
-у=17-3х,
2х+3у=-7;
у=-17+3х,
2х+3(-17+3х)=-7;
у=-17+3х,
2х-51+9х=-7;
у=-17+3х,
2х+9х=-7+51;
у=-17+3х,
11х=44;
х=4,
у=-17+12;
х=4,
у=-5.