Remark
Nicely shown with the brackets so we know exactly what the question is.
You must remember that the division takes place on all 3 terms. You can't leave anything out. You must also remember that since nothing will combine now, nothing will combine in your answer.
[tex] \frac{n^5}{n^3}-\frac{18n^4}{n^3}+\frac{3n^3}{n^3}[/tex]
= n^2 - 18n + 3
Method Two.
I almost hesitate showing you this because you may not have taken it yet, but keep in mind that you can take you a common factor like this.
n^3(n^2 - 18n + 3)/ n^3 The n^3 cancel.
n^2 - 18n + 3