just use the y=mx+c
to find gradient use
m= y2-y1/x2-x1
for example y2=10 y1=4 so y2-y1=6..
and the same thing goes for the x..
C the y-intercept.. I usually just see where it cuts the Y-axis.. but if you can find the equation of the line then you should be able to find the y-intercept.
y-y1=m(x-x1) equation to find a line.. I like using this one.. Hope it helped