5•(8y-1)-7•(4y+1)+8•(7-4y)=9

Ответ:

5 \times (8y - 1) - 7 \times (4y + 1) + 8 \times (7 - 4y) = 9 \\ 40y - 5 - 28y - 7 + 56 - 32y = 9 \\ - 20y = 21 \\ y = - \frac{21}{20} = - 1 \frac{1}{20} = - 1.05