Answer:
[tex]-8j^3+j+2s^3[/tex]
Step-by-step explanation:
The trick here is to consider [tex]j^3[/tex], [tex]j[/tex], and [tex]s^3[/tex] as separate variables.
[tex](4j^3-7j+2s^3)-(-12j^3-8j)[/tex]
[tex]4j^3-7j+2s^3+12j^3+8j[/tex]
[tex]4j^3+12j^3-7j+8j+2s^3[/tex]
[tex]16j^3+j+2s^3[/tex]