Let's first look only at the numerator: 5x^2 - 5
Consider this question: What do both terms have in common?
The answer is 5, both terms contain a 5, so we can factor it out.
5(x^2 - 1)
Now let's look at the denominator, considering the same question: 3x^2 + 3x
This time, both terms contain a 3 and an x.
3x(x^2 + 1)
Now we are here: [ 5(x^2 - 1) ] / [ 3x(x + 1) ]
In the numerator, the binomial factors out into (x + 1)(x - 1). There is also an (x + 1) in the denominator, so those to binomials cancel out. That leaves us with the following expression:
5(x - 1) / 3x
Correct Answer: C
Hope this helps!