Good, but needs work
This is some good base work, though there a few things I have to pick at. For one, the girl on the left, her breasts are too high on the chest, this is likely due to the fact that the torso appears to be a too short. The overall structure looks good so if you were to 'stretch' the torso so to speak, it would look more accurate.
The girl on the right has a better build in her chest, however her head is much too small, her breasts are about the same size as her head. If possible I'd see if you can get any nude photos to sketch from as it could help you figure out the overall proportions. Other than that I can tell that you have a generally good sense of what's going on.
Something else I have to add is that shading on the girl on the right looks pretty nice.
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