To solve the equation \(-12(x + 10) = -\frac{1}{2}(x + 10) = -3\), we should first focus on simplifying both sides.
Since both sides of the equation have a term that contains \((x + 10)\), one effective initial step could be to eliminate those terms, specifically by considering a common operation to isolate \(x\). However, since the equation is already set up for direct solution, let's focus on the options listed:
Among the options you provided, the operation that should be done first to isolate the variable is multiplying by -2. This action helps simplify the equation by getting rid of the fractions and making it straightforward to solve for \(x\).
Thus, the correct answer is:
multiply by -2.