Answer:
-1
Explanation:
The only variable in this expression is y and it's coefficient, which is the number and it's sign before the term, is -1.
In the expression, 6 and 3 are constants. This is because they have a fixed value and they do not change.
However, the algebraic term y can have different values depending on the equation it is in and is thus known as a variable term.
Although the number '1' is not written, it is implied that the digit 1 (or in this case -1) is there. For example, instead of writing 1x, we can simply write x. The coefficient cannot be zero as if there is zero y, the y term would not exist in the first place.