The slope is the change in rise over the change in run.
The formula is given by
m = ( y2-y1)/(x2-x1)
A line going down from left to right has a negative slope
A line going up from left to right has a positive slope.
Given two points on a line
( 4,7) and (3,10)
We can find the slope
m = ( y2-y1)/(x2-x1)
= (10 -7)/( 3-4)
= 3/-1
= -3
This has a negative slope and will go down from left to right.