Final answer:
The correct algebraic equation that represents the situation where the animal shelter receives 18 stray cats and needs to return to its original capacity is Capacity - 12 + 18 = Capacity. None of the provided options in the question exactly match the situation.
Step-by-step explanation:
The animal shelter had a certain capacity for cats, and initially, they had 12 fewer cats than this capacity. After they received 18 stray cats, they went above their capacity and now need to find families to adopt some cats to return to their original capacity. The correct equation to represent this scenario is Capacity - 12 + 18 = Capacity. This equation shows that the shelter's capacity, minus the 12 cats they initially had room for, plus the 18 stray cats they received, will bring them back to their original capacity. The correct option from the list given in the question is therefore not listed, but the implied equation that matches the situation is: Capacity - 12 + 18 = Capacity.