Answer:
3x
Step-by-step explanation:
[tex] \sqrt{9 {x}^{2} } [/tex]
[tex] \sqrt{9} \sqrt{ {x}^{2} } [/tex]
[tex] \sqrt{ {3}^{2} } \sqrt{ {x}^{2} } [/tex]
[tex] \sqrt{ {3}^{2} } x[/tex]
[tex] = 3x[/tex]
