1 дробь
(x^2 + 12x + 27)/(3x^2 + 9x) = (x+3)(x+9)/[3x(x+3)] = (x+9)/(3x)
2 дробь
(x^2 - 4x - 45)/(3x^2 + 15x) = (x-9)(x+5)/[(3x(x+5)] = (x-9)/(3x)
Вычитаем:
(x + 9)/(3x) - (x - 9)/(3x) = (x + 9 - x + 9)/(3x) = 18/(3x) = 6/x
Теперь подставляем х = 0,3.
6/x = 6/0,3 = 60/3 = 20