Answer:
x = -4
Step-by-step explanation:
An undefined slope would look like a vertical line, up and down. This is shown using an x equals equation instead of a y equals equation.
Since the line goes vertically, you only need to look at the x-value to make the equation, since after doing x = -4 the line would keep going down until it touched (-4, -8).
The line would touch everything in the y-value but stay at x = -4.
Therefore the answer to this problem is x = -4. I've attached a picture (from desmos) showing what the graph of x = -4 would look like and how it touches the point (-4, -8).
The formula for circumference is 2

r, where r is equal to radius.
It states to use 3.142 for pi
It also provides you with the diameter, not the radius, so you have to divide it by two to get 4.5
2*3.142*4.5= approximately 28.278 or 28.3
You'll multiply the both incomes and then reduce them to the lowest form.
1/10 * 2/9 = 2/90
Reduce it:
2/90 = 1/45
So the assistant gets 1/45 the income of the athlete.
Hope this helps :)