You can
put this solution on YOUR website!
2 < 3d-4 < 15
Add 4 to all three sides, to get 3d alone in the middle
2 < 3d-4 < 15
+4 +4 +4
6 < 3d < 19
Divide by 3 to get d alone in the middle:
6/3 < 3d/3 < 19/3
2 < d < 6 1/3
The only integers that are between 2 and 6 1/3 are these:
3,4,5 and 6
Edwin