M-9n/n+n/m m/n=1/3 помогите решить

(m - 9n) / n + (n / m) = (m (m - 9n) + n^2) / mn = (m^2 - 9mn + n^2) / mn

m / n = 1/3

n = m : 1/3

n = 3m

(m^2 - 9m•3m + 9m^2) / 3m^2 = ( - 17m^2) / 3m^2 = - 17/3 = - 5 2/3

Ответ ( - 5 2/3)