Hello LUANDATO.

Let's take a look at your question.

The area of a square is equal to L² where L is the lenght of the side of the square.

So, we have $$L^2=\frac{9P^2}{16},$$

this implies that $$L=\frac{3P}{4}.$$

Now, the perimeter of a square is 4L. It is, $$Perimeter=4L=4\cdot\frac{3P}{4}=3P.$$

So, the correct asnwer is C.

I hope this answer can help you.

Example:

Let be P=2, so the area of the square is A=9*4/16.

It implies that the side of the square is equal to 3*2/4. Now, the perimeter is 4*(3*2/4)=3*2.

On the other hand, 3*2=3*P.

I'm available if you'd like any follow up.

Thank you so much for your help! Now, it's so clear to me! Great, I'll have on mind!