Y=2x+B
Using the equation rise/run you input your coordinates in the form of y2-y1/x2-x1 to arrive at your slope.
Next you write the equation Y=mx+b and substitute on one set of coordinates into the problem.
I used (1,2)
2=2(1)+ b
subtract 2 on both sides
0=b
rewrite your final equation y=2x+0 also written as y=2x :)