Use y = mx + b.
m represents the slope of the line.
the slope equals rise over run.
in other words, count the number of vertical and horizontal units from one point to another point on the line.
if you have the y-intercept and a point, you can also solve for m.
b represents the y-intercept.
find the point on the graph where x = 0.
b is the value of y.
for example, if the y-intercept was (0,4) then b would equal 4.
x and y represent a point on the graph.
pick any point on the graph and plug it in.
for example, if the point (1,2) is on the graph then x = 1 and y = 2.