To solve the equation \(-3(y + 6) = 21\) for \(y\), the first step is to divide both sides by \(-3\).
So the equation becomes:
\[ y + 6 = -7 \]
The second step would be to subtract 6 from both sides to isolate \(y\).
Therefore, the correct response indicating the second step is:
Subtract 6 from both sides.