The quotient of - 15 and w

If you're dividing - 15 by w then the answer would be - 15/w. This is because the value of w has not been determined yet and a number cannot be divided by a variable.

If you're dividing w by - 15, the same situation would occur due to the fact that a variable cannot be divided by a number. The answer would be w/-15.

A variable is merely a "placeholder", for lack of better terms, for a number (s) that have not been identified yet.

I hope I cleared this up!