Answer:
[tex]5.5\:\mathrm{m}[/tex]
Explanation:
We can use Newton's Universal Law of Gravitation to solve this:
[tex]F=G\frac{m_1m_2}{r^2}[/tex],
Plugging in given values, we have the equation:
[tex]4.7\cdot 10^{-10}=6.67\cdot 10^{-11}\cdot \frac{12\cdot 18}{r^2}[/tex].
Solving, we get:
[tex]r^2=30.6536,\\r=\fbox{$5.5\:\mathrm{m}$}[/tex].