Answer:
-x-15
Explanation:
x-2x-15
1x-2x-15 (if a term doesn't have a coefficient then the coefficient is 1)
(1-2)x-15 (collect like terms by subtracting their coefficients)
-1x-15
-x-15 (when the term has a coefficient of -1, the number doesn't have to be written but the sign remains)