54х+у=20
127х+2у=20
-108х-2у=-40
19х=-20
х=-20/19
54*(-20/19)+у=20
у=1460/19
(х,у)=(-20/19, 1460/19)
54*(-20/19)+1460/19=127*(-20/19)+2*1460/19=20
20=20=20
(х,у)=(-20/19,1460/19)
