<u><em>Answer:</em></u>5n-4
<u><em>Explanation:</em></u><u>The given expression is:</u>

<u>1- Take the negative as a common factor from both the numerator and the denominator. This will give us:</u>

<u>2- Cancel out the negative sign (common factor) from the numerator and denominator. This will give us:</u>

<u>3- Factor the numerator. This wil give:</u>

<u>4- Finally, cancel out the (17n+19) which common in both numerator and denominator. This will give us the final expression:</u>
5n-4
Hope this helps :)
You have a lot of questions here, I can help you with a few of them.
When you simplify the polynomials, you put together all of the terms that have the same degree. That means the variables have the same exponents. The number of terms are the items separated by plus and minus signs.
Here are the answers for the first three:
1)

2)

3)