I was trying to solve this system and I tried to express $y = \frac{100}{x}$ from the first equation and change into the second one and I got $\frac{100}{x}\log_{10}{x} = 10$ After some work I got to $x = 10\log_{10}{x}$ And I cannot solve this one.
$\begin{cases}xy = 100 \\ y\log_{10}{x} = 10\end{cases}$
Hint: From the second equation we get $$y=\frac{10}{\log_{10}{x}}$$ plugging this in the first one $$\frac{x}{\log_{10{x}}}=10$$ so $$x=10\log_{10}{x}$$ Here you will need a numerical method. From here we get the simpler equation $$10^{x/10}=x$$ With $$y=\frac{10}{\log{10}{x}}$$ we get
$$\frac{10x}{\log_{10}{x}}=100$$