Ответ:

а) \(\frac{13}{225}:\frac{169}{115}=\frac{13}{225}\cdot\frac{115}{169}=\frac{23}{585}\).

б) \(\frac{7a^{15}}{b^7}:\frac{21a^{16}}{b}=\frac{7a^{15}}{b^7}\cdot\frac{b}{21a^{16}}=\frac{1}{3ab^6}\).

в) \(2b:\frac{3b^2}{a+b}=2b\cdot\frac{a+b}{3b^2}=\frac{2(a+b)}{3b}\).

Ответ: а) \(\frac{23}{585}\); б) \(\frac{1}{3ab^6}\); в) \(\frac{2(a+b)}{3b}\).