The leaves of three mean it could be the notorious poison ivy that not everyone is allergic to. I suggest you put a sample into a ziplock bag and take it to a Master Gardener clinic or local nursery for a more accurate ID. It is hard to tell without seeing the entire plant. You are on the right track about getting rid of it. Just keep pulling it up and you will win. Keep growing, (but not weeds) Marianne Binetti