We have been given the steps to solve the equation as
Step 1: 2x = 18
Step 2: x = 18 − 2
Step 3: x = 16
There is an error in step 2.
We have 
x is in multiplication with 2. So in order to get rid of 2 from the left hand side, we perform opposite operation of multiplication i.e. division.
So we must divide both sides by 2.
Therefore, A is the correct option.
A) She did not divide 18 by 2.
Given t = time and h = height

From the equation.

h is the axis od symmetry
(h, k) is the vertex.
In the equation, h is 1 and k is 16.
So the maximum value is 16 at t = 1.
The ball reaches maximum at 16 and it takes t = 1 to reach the maximum point.
Answer:
233.33 mg
Step-by-step explanation:
9x = 2100
---> x = 2100/9
---> x = 233.33 mg
There are no given coordinates, so it's impossible to answer your question. I'm sorry.