Объяснение:

[tex]\frac{3x}{y}*\frac{y}{15x}=\frac{1}{5}\\\frac{26p^7}{51c^5}*\frac{34c^3}{39p^4}=\frac{2p^3}{3c^2}*\frac{2}{3}=\frac{4p^3}{9c^2}\\20y^6*\frac{3x^3}{5y^9}=4*\frac{3x^3}{y^3}=\frac{12x^3}{y^3}\\\frac{2ab-b^2}{3}*\frac{9a}{b}=b(2a-b)*\frac{3a}{b}=(2a-b)*3a=6a^2-3ab\\\frac{x^2-25}{x^3-6x^2}*\frac{x^2-9}{x^2+4x}=\frac{(x^2-25)(x^2-9)}{(x^3-6x^2)(x^2+4x)}=\frac{x^4-9x^2-25x^2+225}{x^5+4x^4-6x^4-24x^3}\\[/tex]