Answer:
The first problem.
Explanation:
-6 + (-6) + (-6) = -18
first problem: 3 · (-6) = -18
second problem: 6 · (-6) = -36
third problem: -3 · (-6) = 18
fourth problem: -6 · (-6) = 36
Therefore, the first problem is equivalent because it had the same answer as the original problem.