Subtractive drawing is a process where the drawing surface is completely covered in graphite or charcoal, then erased to make the image.
Printing is a subtractive process; all the colors combine to form black.
modelling
An additive process is one that adds on material to an existing part or solid object to make it larger in mass. A subtractive process is one that shoves down material off of a part or solid object in order to make it smaller or lighter weight.
Boron
Do your work on your own. Research. Read what you're supposed to.