Thank you for reporting, we will resolve it shortly
Q.
If $x, y$ and $z$ be greater than $1$, then the value of $\begin{vmatrix}1&log_{x}\,y&log_{x}\,z\\ log_{y}\,x&1&log_{y}z\\ log_{z}\,x&log_{z}\,y&1\end{vmatrix}$ is
$\begin{vmatrix}\frac{log\,x}{log\,x}&\frac{log\,y}{log\,x}&\frac{log\,z}{log\,x}\\ \frac{log\,x}{log\,y}&\frac{log\,y}{log\,y}&\frac{log\,z}{log\,y}\\ \frac{log\,x}{log\,z}&\frac{log\,y}{log\,z}&\frac{log\,z}{log\,z}\end{vmatrix}$
Taking $\frac{1}{log\,x}, \frac{1}{log\,y}, \frac{1}{log\,z}$ common from $R_1, R_2, R_3$ all rows are identical. So $\Delta =0$