They're very nice! I don't have much feedback for the last two images, but there's one thing that strikes me in the first drawing.
In the two other sketches you have some pretty fluid lines going, as well as object interaction. I miss both in the first sketch. While you did a good job on focusing on the upper body anatomy, the legs just feel misplaced, like they're there to fill up space but aren't part of the figure. Unlike the other drawings, this one has no flow of motion in it. There's nothing to interact with either to counter this lack of motion. It makes it feel a little static and doesn't catch the eye quite so much.