Раскроем скобки:
\[0.2(5y-2)-0.3(2y-1)=-0.9\]
\[y-0.4-0.6y+0.3=-0.9\]
\[0.4y-0.1=-0.9\]
\[0.4y=-0.8\]
\[y=-2\]
Ответ: \(y=-2\).