(-3)(7) = -21.
y^8 and c^3 have different bases (y and c) and thus cannot be merged.
So we end up with -21c^3y^8.
Answer:
[tex]\large\boxed{-21c^3y^8}[/tex]
Step-by-step explanation:
[tex]-3y^8\cdot7c^3=(-3\cdot7)(y^8c^3)=-21c^3y^8[/tex]
