Ответ:

  1. \[\frac{3a}{b}\cdot\frac{b}{15a}=\frac{3ab}{15ab}=\frac15.\]
  2. \[\frac{mn^3}{24p}\cdot\left(-\frac{6p}{m^2n}\right)=-\frac{6mn^3p}{24pm^2n}=-\frac{n^2}{4m}.\]
  3. \[\frac{26x^7}{51y^5}\cdot\frac{34y^3}{39x^4}=\frac{26\cdot34x^7y^3}{51\cdot39y^5x^4}=\frac{4x^3}{9y^2}.\]
  4. \[20m^6\cdot\frac{3x^3}{5m^9}=\frac{60m^6x^3}{5m^9}=\frac{12x^3}{m^3}.\]
  5. \[\frac{25k^6}{11p^3}\cdot44p^9=\frac{25\cdot44k^6p^9}{11p^3}=100k^6p^6.\]
  6. \[\frac{3x^3y^2}{8m^2n}\cdot\frac{16xm^3}{27y^4n^8}\cdot\frac{18n^2y^2}{4x^2m}=\frac{3\cdot16\cdot18\,x^4m^3y^4n^2}{8\cdot27\cdot4\,x^2m^3y^4n^9}=\frac{x^2}{4n^7}.\]

Ответ: 1) \(\frac15\); 2) \(-\frac{n^2}{4m}\); 3) \(\frac{4x^3}{9y^2}\); 4) \(\frac{12x^3}{m^3}\); 5) \(100k^6p^6\); 6) \(\frac{x^2}{4n^7}\).