Question 255950
Remember that if you have a slope m and a point (x1,y1), the equation for the line is:

y-y1=m(x-x1)

So for the first problem we have m=2 and (x1,y1)=(2,4).  So we have:

y-4=2(x-2)
y-4=2x-4
y=2x

The next two are similar, so this should help you complete that.  For the question about slope, if you have two points (x1,y1) and (x2,y2) the slope is:

{{{m=(y2-y1)/(x2-x1)}}}