For questions #6 & #8, you didn't complete them or provide all necessary things (such as description, data, or graph). 5 − ≤ 20 is not an inequality, an inequality should be something like 5 - x ≤ 20, but you didn't give anything like that in your question.
7. (-1,4), (5,2), we can calculate the slope. As x increases from -1 to 5, (increases by 6), the y-value decreases by 2. -2/6 = -1/3, the slope is -1/3. The slope is negative and the y-value decreases by a third of the amount the x-value changes.
9. C, because you can only hold at MOST 500, and larger watermelons is represented by 10x. I'm assuming you made an error in your question, you gave me the values of larger/smaller watermelons only, and your question asked for larger & medium and the options seem to suggest there's only larger/smaller. 10x + 3y <= 500 or <, smaller than or equal would be the better choice if available.
10. y = 2x + 10, because 2 is the slope as minutes increase by 1, inches increase by 2, and the 10 inches of sawdust are already there.
When you offer Questions #6 & #8's data, I'll gladly help you with it. The rest of the questions are correct and properly explained.
The sum of a number is the answer to an equation of a number plus a number you are correct.
Answer:

Variable is a symbol that represents a quantity in a mathematical expression, as used in many sciences. Variable (research), a logical set of attributes. Variable star, a type of astronomical star.

A constant, sometimes also called a "mathematical constant," is any well-defined real number which is significantly interesting in some way. A function, equation, etc., is said to "be constant" (or be a constant function) if it always assumes the same value independent of how its parameters are varied.
Answer:
27.44
Step-by-step explanation:
area of the half sircle = 12.56
area of the rectangle = 40
area of the shaded protion = 40 -12.56
=27.44 square yards
Answer:
The answer to your question is: 3x³ - x² - 4x - 2
Step-by-step explanation:
Data
3x⁴ + 2x³ - 5x² - 6x - 2
x + 1
Process
Synthetic division
3 2 -5 - 6 -2 -1
-3 1 4 2
3 -1 -4 -2 0
Result 3x³ - x² - 4x - 2