Good job, Tim
Now it is correct for the subject matter of this class. But in reality the VP's of the left dice will lie further apart. The nearest corner of a cube can never - NEVER - be sharper than 90°. When you look completely down on it, it is 90°.
I've no experience with Painter, it could be that you have to do it the other way round, first cropping.
GIMP is very powerful, hence a large documentation. But the simple operations - cropping, scaling, rotating, straight lines, improving the contrast - are rather obvious if you have some experience with other graphic software. There is a very good online handbook
You did very well in this class, please move on to class 4