Can somebody me simplify this expression on #14 ? explain as well!

In the numerator, you can simplify x^2-9 into (x+3)(x-3), and in the denominator, you can pull out a GCF of x^2, leaving you with x^2(x-3). After this, you may notice that both the numerator and denominator contain (x-3); you can cancel them out, and you are left with (x+3)/x^2.

What’s the question here? what have you been learning about?