Answer:
[tex]19m + 13c[/tex]
Step-by-step explanation:
Step 1: Combine like terms
[tex]-m + 17m - 12c + 3m + 4c + 21c[/tex]
[tex](-m + 17m + 3m) + (-12c + 4c + 21c)[/tex]
Answer: [tex]19m + 13c[/tex]