Question 120553
First, note the general formula for a slope :

{{{m = ((DELTA)y)/((DELTA)x)}}}

This means that a slope gives the change in y with respect to the 
change in x. We use {{{(DELTA)}}} to mean "change."

Now, 

{{{m = (y[2] - y[1])/(x[2] - x[1])}}}

In the example, we have the starting point of (0, 
  0) and end point (3.25, -1800). It is key that you understand these two points. You start at a position where you have not moved at all (0,0). You then move to your second position which was given in the problem--- 3.25 horizontal change, 1800 negative change--- (3.25,-1800).

Plugging this into our equation for a slope :

{{{m = (-1800 - 0)/(3.25 - 0) = -553.8461538461539...}}}

which is approximately equal to {{{-553.85}}}