20log(1/x)=20

$${\mathtt{20}}{\mathtt{\,\times\,}}{log}_{10}\left({\frac{{\mathtt{1}}}{{\mathtt{x}}}}\right) = {\mathtt{20}} \Rightarrow {\mathtt{x}} = {\frac{{\mathtt{1}}}{{\mathtt{10}}}} \Rightarrow {\mathtt{x}} = {\mathtt{0.1}}$$