(0.4k3 – 2.5k) – (2.4k3 + 3k2 – 1.2k) = –2.8k3 – 3k2 – 3.7k –2.8k3 + 3k2 – 1.3k –2k3 – 3k2 – 1.3k –2k3 + 3k2 – 3.7k

its –2k3 – 3k2 – 1.3k that's what it is for sure