Recall that:
[tex]\begin{gathered} \text{For all x}\in\R \\ \sqrt[]{x^2}=|x|\text{.} \end{gathered}[/tex]Therefore:
[tex]3\sqrt[]{c^2}=3|c|\text{.}[/tex]Now, since c≥0, we get that:
[tex]|c|=c\text{.}[/tex]Substituting the above result in 3|c| we get:
[tex]3\sqrt[]{c^2}=3c\text{.}[/tex]Answer:
[tex]3c\text{.}[/tex]