Dude, excluding the first few pics, these are from a commercial site that guarantees the model's ages are 18+. In case you were wondering the site, look at the pics. Think before you post, and be nice to people.
I agree the first couple look iffy...
However I have seen many girls certified 18 on paysites who look like they're in their mid-teens. I guess there is no sure way to tell, but unless there is some proof of their age, such as being from a site who does their own photography, it's best not to post girls who look like their in their tweens.