Part A: Yes, the data represent a function. The definition of a function is a relation in which no value of x will have two different values of y.
(Every time you plug in 3 as x, you will always get 4 as y; it's ok if you plug in 3 and 5 as x and get the same y, you just can't get two different y's for one x; sorry, it is pretty confusing). None of the numbers in the table repeat, so we can safely say that the relation is a function.
Part B: All we have to do is plug in 11 for x in the function given to find the answer:

In the table, y = 8 when x = 11, but in the function given, y = 34 when x = 11, so the function given is greater.
Part C: To find the answer to C, just plug in 99 for f(x), as it tells you to do:
81300 - 56800 = 24500....so she made 24500 in passive income for the year.
We need per month, so we divide by 12 because there is 12 months in a yr.
24500/12 = 2041.67 per month
Should be 7 feet. 6+6=12 then 26-12=14, divide that by 2 (for the other two sides of the rectangle), you'll get 7 ft.
x+6 is x+6. It's an expression. Not sure what you need help with.