\(\quad\,\frac{1}{\sqrt{8}+\sqrt{50}+\sqrt{18}} \\~\\ =\,\frac{1}{2\sqrt{2}\,+\,5\sqrt{2}\,+\,3\sqrt{2}} \\~\\ =\,\frac{1}{10\sqrt{2}} \\~\\ =\,\frac{1\,\cdot\,\sqrt2}{10\sqrt2\,\cdot\,\sqrt2} \\~\\ =\,\frac{\sqrt2}{10\,\cdot\,2} \\~\\ =\,\frac{\sqrt2}{20}\)
.