Решение:

1. $$\frac{4p}{t} - \frac{2t}{5p} = \frac{4p \cdot 5p - 2t \cdot t}{5pt} = \frac{20p^2 - 2t^2}{5pt}$$

   Ответ: $$rac{20p^2 - 2t^2}{5pt}$$

2. $$\frac{6f-9}{9fx} - \frac{x-3}{3fx} = \frac{6f-9 - 3(x-3)}{9fx} = \frac{6f-9 - 3x + 9}{9fx} = \frac{6f - 3x}{9fx} = \frac{3(2f-x)}{9fx} = \frac{2f-x}{3fx}$$

   Ответ: $$\frac{2f-x}{3fx}$$

3. $$\frac{6b-7}{7} + \frac{b-8}{3} = \frac{3(6b-7) + 7(b-8)}{21} = \frac{18b-21 + 7b - 56}{21} = \frac{25b - 77}{21}$$

   Ответ: $$\frac{25b - 77}{21}$$

4. $$\frac{4x+4}{5y} + \frac{3x-3}{4y} = \frac{4(4x+4) + 5(3x-3)}{20y} = \frac{16x+16 + 15x - 15}{20y} = \frac{31x + 1}{20y}$$

   Ответ: $$\frac{31x + 1}{20y}$$

5. $$\frac{4}{3d} - \frac{9a}{5y} = \frac{4 \cdot 5y - 9a \cdot 3d}{15dy} = \frac{20y - 27ad}{15dy}$$

   Ответ: $$\frac{20y - 27ad}{15dy}$$