y= mx+b
m = the value of the slope
b = the y - intercept
To solve for m or the slope you can either count the graph .. How many units it went up or down or to the right or left ..
Also know as rise / run
Other way you can do it is by ... If there are two different corrdinates given and they ask you to find the value of slope..
you use the formula .. y^2 - y^1 / x^2 - x^1
For example if there is .. (-1 , -3) , (2 , 5) and you are asked to find the slope.. * I attached the picture of the example*
Hope it helps