Answer:
C. 
Step-by-step explanation:
I think the equation meant
?
Anyways, to factor these kinds of quadratic, keep into consideration:

ONLY if:

Start off by finding factors of c, which in this case, -18:
±(1, 2, 3, 6, 9, 18)
If one of the numbers is negative then the other number must be positive.
Find which two factors will sum up to b, which in this case, is 3.

The only two factors that work are 6 and -3.
Replace them into the factored form:

Remark.
The problem is a bit indistinct. Where exactly are the two edges of the road? I'm going to say that they are the x intercepts, but that may not be true. Certainly it does not have to be true at all.
Graph.
A graph has been made for you. The maximum is marked for you. It is an approximation The actual height can be more accurately found.
Height
y = (-1/200)(x - 16)(x + 16)
y = (-1/200)*(x^2 - 256)
The maximum height for this graph only is when x = 0.Other graphs require completing the square.
y = (-1/200) * (-256)
y = 1.28 exactly. I thought the graph might be rounding the answer. It is not.
Answer:
associative = (2 + 6) + 3 = 2 + (6 + 3)
commutative = 8x4=4x8
distributive is the one with 2(3+7)
identity of addition 9+0
identity of multiplication (16)(1)