These two terms are what we call, 'like terms'. This means that they are terms whose variables and exponents are the same. 14w^9- 19w^9 have the variable w^9 in common.
In these cases, all we do is use the coefficients (the number in front of the variable). Hence, 14w^9- 19w^9, quite literally turns into, 14-19. If we complete the sum, 14-19= -5. Put it all together, we have -5w^9.
