(9s^4 - 4s + 5) + (2s^4 - 6 + s^5) - (7s^5 - 8)

(9s^4 - 4s + 5) + (2s^4 - 6 + s^5) - (7s^5 - 8)

9s^4 - 4s + 5 + 2s^4 - 6 + s^5 - 7s^5 + 8

9s^4+ 2s^4 - 4s + 5 - 6+ 8 + s^5 - 7s^5

11s^4 - 4s +7 - 6s^5