Tenemos que:

\[ \begin{aligned} \sqrt{0.000036} &= \sqrt{ \frac{36}{1000000} } \\[2em] &= \sqrt{ \frac{36}{10^6} } \\[2em] &= \frac{ \sqrt{36} }{ \sqrt{10^6} } \\[2em] &= \frac{6}{10^3} \\[2em] &= \frac{6}{1000} \end{aligned} \]

Luego,

\[ \begin{aligned} x \sqrt{0.000036} = 6 &\Rightarrow x \frac{6}{1000} = 6 \\[2em] &\Rightarrow x = \frac{ 6 \times 1000 }{6} \\[2em] &\hspace{2em}= \boldsymbol{1000} \end{aligned} \]