The first thing that we want to do is factor the quadratic expression in the numerator.
4x2 - 15x + 9
(4x - 3)(x - 3)
Now, we have the following equation:

Now, both numerator and denominator have an (x-3), so you can divide (x-3) from the numerator


So, we are left with 4x-3
Hope this helped!! :D