Ответ:

[tex] \frac{y + 1}{2} + \frac{7y - 7}{5} - \frac{9 - y}{10} = 1[/tex]

[tex] \frac{5(y + 1)}{10} + \frac{2(7y - 7)}{10} - \frac{9 - y}{10} = 10[/tex]

[tex] \frac{5y + 5 + 14y - 14 - 9 - y}{10} = 10[/tex]

[tex]5y + 5 + 14y - 14 - 9 - y = 10[/tex]

[tex]20y - 18 = 10[/tex]

[tex]20y = 10+ 18[/tex]

[tex]20y = 28[/tex]

[tex]y = \frac{28}{20} = \frac{7}{5} [/tex]