Răspuns: D.18
Explicație pas cu pas:
[tex]n=\sqrt{\not{54}\cdot\frac{6}{\not{9} }}+\sqrt{\not{540}\cdot\frac{6}{\not{90}} } +\sqrt{\not{5400}\cdot\frac{6}{900} } \\\\n=\sqrt{36} +\sqrt{36} +\sqrt{36} \\\\n=6+6+6\\\\\boxed{n=18}[/tex]
