Question

Need help understanding what to do

Answer 1

I believe you are expected to simplify. To do this all you do is group like terms (x, x², x³ etc.) and then simplify the coefficients. 

13. 10z + 7z - 19z² - 5z² - 17z 

first you can rearrange and group like terms (remember the bring the sign in front of each term with it). I would do it like this: 
-19z² - 5z² +10z + 7z - 17z

Now simplify the coefficients: 

-24z² + 0z 

you can omit the 0z and your simplified answer is 

-24z²

Main thing to remember here is that z and z² cannot be simplified together, nor can any variable that has an exponent because the exponent makes them differ.