2.7+3у=9(у-2.1)

2.7+3у=9у-18.9

3у-9у=-18.9-2.7

-6у=-21.6

у=3.6

0.3(8-3у)=3.2-0.8(у-7)

2.4-0.9у=3.2-0.8у+5.6

2.4-0.9у=8.8-0.8у

-0.9у=0.8у=8.8-2.4

-0.1у=6.4

у=-64