And here’s the second pic for the Brainly

Answer:
3a³ -20a² +16a -24
Step-by-step explanation:
Unlike the other problems shown here, this one requires you combine like terms.
= a(3a² -2a +4) -6(3a² -2a +4)
= 3a³ -2a² +4a -18a² +12a -24
= 3a³ -20a² +16a -24