The slope of two parallel lines are equal.
Let us find slope of given equation.
The general slope intercept form is given by :

where m is slope
our equation is :

Now we have to convert our equation into slope intercept form.
let us try to isolate y on the left side.
taking 5x to the right side we have ,

dividing both sides by -15,

coefficient of x is slope,
so slope is 1/3
slope of line parallel to it is also same that is 1/3 .
Correct option is D.