If we write y in terms of x we get y=-(15+5x)/3=-5(3+x)/3.
Each ordered pair on the line 5x+3y=-15 can be represented by (x,-5(3+x)/3).
By substituting values for x we get numerical ordered pairs; for example:
if we put x=0, 1, 2, 3, 4 we get pairs (0,-5), (1,-20/3), (2,-25/3), (3,-10), (4,-35/3).