$$\frac{x+1}{2y} - \frac{5x-6}{2y} = \frac{x + 1 - (5x - 6)}{2y} = \frac{x + 1 - 5x + 6}{2y} = \frac{-4x + 7}{2y}$$
Ответ: $$\frac{-4x + 7}{2y}$$