There are many different ways of representing the equation of a line. With the given information, the best form of the equation to use is point-slope form which can be written as 

 where 

 is the x and y coordinates of a given point on the line and 

 is the slope of the line. Since you are given that the slope of the line is 3 and has the point (-1,-8), the equation should look like 

, which is letter choice D.