Answer :
[tex]a)\\\\ \sqrt {45}=\sqrt{9\cdot 5}=\sqrt{9}\cdot \sqrt{5}=3\sqrt{5}\\\\b)\\\\ \sqrt{54}=\sqrt{9\cdot 6}=\sqrt{9}\cdot \sqrt{6}=3\sqrt{6}\\\\c)\\\\\sqrt{\frac{16}{25 } }=\frac{\sqrt{16}}{\sqrt{25}}=\frac{4}{5}[/tex]
