The rules are ...
[tex]\Longrightarrow \ln(\frac{a}{b})=\ln(a)-\ln(b)[/tex]
[tex]\Longrightarrow \ln(a^{b})=b\ln(a)[/tex]
Your expression makes use of both these rules.
[tex]3\ln(x)-5\ln(c)=\ln(x^{3})-\ln(c^{5})=\ln \left( \dfrac{x^{3}}{c^{5}} \right)[/tex]
Your single logarithm is ...
[tex]\ln \left( \dfrac{x^{3}}{c^{5}} \right)[/tex]
