In equations, the terms (either a number, letter or combination of both) are given a sign (either positive or negative) which is initially 'attached to the term'. In the above equation in JD's post there are three terms: -2, +5x and +63. Addition and subtraction don't really come into it until you start manipulating the equation in order to solve it.
Edit: Subtraction is an operation. Something being negative is different and you need to identify the difference between the two.