Answer :
If the line is parallel, the slope must also be 1/3.
Plug in the coordinates of (0,-9) into y=1/3x+b:
1) -9=(1/3)(0)+b
2) -9=0+b
3) b=-9
Plug in the coordinates of (0,-9) into y=1/3x+b:
1) -9=(1/3)(0)+b
2) -9=0+b
3) b=-9
