First you need to identify and group like terms.
You should rewrite d and 1d and group the coefficients together and you will have (-5 + 1) d + (-8 - 9)
Then combine - 5 + 1 to get - 4 so then you would have -4d + (-8 - 9)
Combine - 8 + -9 to get -17 after all you will end up with -4d - 17
Answer: -4d - 17
