How do I cheaply paint walls that duct tape stripped and ruined?
From looking at the pics, I don't think the walls are specially textured. Looks like typical "orange peel" finish from rolling on the paint.  I think all you really need to do is fill the voids where the two layers of paint have been removed with some "Light Weight Spackle". Light weight spackle is very cheap and can fill small blemishes quickly and easily. Apply with a small putty knife, let it dry for 20 minutes then sand it or smooth it with a damp sponge. Get a sample of the color from the tape, or peel a small piece from the wall and get a pint mixed at any paint dept. Have the paint sales person determine what finish the paint is, I suspect egg shell or satin.  You can use a mini roller or a soft brush to apply some over your patched areas, overlapping the undamaged color a bit. It may take a few light coats.  Try to "feather" the edges into the existing color by using very light pressure on your roller or brush as you overlap the original color.   Good Luck.