Use the Laws of logarithms to rewrite the expression
ln(x18y8z5)\displaystyle {\ln{{\left({x}^{{{18}}}\sqrt{{{\frac{{{y}^{{{8}}}}}{{{z}^{{{5}}}}}}}}\right)}}}
in a form with no logarithm of a product, quotient or power.
After rewriting we have
ln(x18y8z5)=Aln(x)+Bln(y)+Cln(z)\displaystyle {\ln{{\left({x}^{{{18}}}\sqrt{{{\frac{{{y}^{{{8}}}}}{{{z}^{{{5}}}}}}}}\right)}}}={A}{\ln{{\left({x}\right)}}}+{B}{\ln{{\left({y}\right)}}}+{C}{\ln{{\left({z}\right)}}}

with the constant
A=\displaystyle {A}=  
the constant
B=\displaystyle {B}=  
and the constant
C=\displaystyle {C}=