3/7(0,56-4,9y)-6/13(0,52-3,9y)=0,6
1) 3/7(0,56-4,9y)=3/7*56/100-3/7*4 9/10у= 6/25-21/10у
2) 6/13(0,52-3,9y)=6/13*52/100-6/13*3 9/10у= 6/25-18/10у
3)6/25-21/10у-6/25+18/10у=-3/10у
-3/10у=0,6
у=6/10:(-3/10)
у=6/10*-10/3
у=-2
3/7(0.56-4.9у)-6/13(0.52-3.9у)=0.6
0.24-2.1у-0.24+1.8у=0.6
-2.1у+1.8у=0.6
-0.3у=0.6
у=0.6:(-0.3)
ОТВЕТ: -2