Use the point-slope formula:
substitute x1=-2, y1=8, m=2,
Don't substitute anything for x and y, leave them variable:
Write (8) as 8 and x-(-2) as x+2
Distribute on the right:
Add 8 to both sides:
Edwin
...or you can use the slope-intercept form instead of the point-slope form. Many students find this easier.
You know the equation is of the form y=mx+b, with m=2; and that the point (x,y) = (-2,8) is on the line. So
The equation is
As you get more comfortable with the subject of linear equations, you can get to the answer without the formal mathematics, starting with the equation y = 2x+b:
The point (-2,8) is on the line;
2 times -2 is -4;
what do I need to add to that -4 to get 8? 12