To solve the equation \(-3(y + 6) = 21\), the first step is to divide both sides by \(-3\) to isolate the term \(y + 6\). Therefore, the second step would be the step that follows after dividing both sides by \(-3\), which is simplifying to solve for \(y\).
The correct response for the second step in the context of the entire solution process is:
Divide both sides by −3.