Well no actually it'd still clear to me that they mean the the multiplication of 3 different variables X, N, and D. I don't think of it as eliding obvious oper

Well no actually it'd still clear to me that they mean the the multiplication of 3 different variables X, N, and D. I don't think of it as eliding obvious operators. Rather in mathematics juxtaposition is used as an operator to represent multiplication. You would never elide an addition operator. So X next to D still means multiplication as long as you can tell that X and D are separate entities. I would wonder why they switched conventions in the middle of an expression though.