No, I think the tree weighs 15 pounds without the pot, cuz it says that the potted tree weighs 35 pounds, so the tree with the pot weighs 35 pounds, and we know that pot is 5 pounds more than the tree. So, if the tree is 15 pounds, then the pot would be 15+5 = 20 pounds, and 20 + 15 is 35. So, I conclude that the tree weighs 15 pounds by itself.
Sorry if I'm wrong.