How do you find slope ?
if you have a slanted line, draw a right triangle with the line as hypotenuse.
Looking at the triangle, the slope of the line is the height/width.
In the x-y plane,
slope is ∆y/∆x
That is, it tells how fast y is changing as x changes. If y increases by 3 every time x increases by 2, the slope is 3/2.
If y decreases as x increases, the slop e is negative.