Using subqueries is alright except in the case of the second problem where i wasn't supposed to use one, but we're already pass that now, so in the case of the remainder of the problems, yes, subqueries can be utilized. And, not using subqueries is fine too, if that's what you favor. Which ever way is good. If you see that using more that a single statement seems best over using a subquery or more is best, than go with that way. I'm unsure of which version this is, but subqueries are supported as well.