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.
Since the problem said he uses 160 feet of fence, you know that is the perimeter
P = 2l + 2w
You know that one of the dimensions is 50, so you can plug that into the equation
160 = 2 x 50 + 2w
160 = 100 + 2w
2w = 60
w = 30
The area is equal to l x w
50 x 30 = 1500 square feet
5/6x -4 = -2
5/6x = 2
multiply both sides by 6 to get rid of the fraction.
5x = 12
x = 2.4
It is C, if it falls 14 ft. and it travels back up 7 ft. and then falls another 7 ft, and stops at the ground now you add it all up 14+7+7=28. hope that helps you.