Give the step-by-step reasoning process and then the final answer. An animal shelter recently took in twelve cats. The shelter already had half that number of cats. Two days later, three had been adopted. The next day, one of the cats had five kittens, and one person arrived to pick up one of the cats that was their missing pet. How many cats does the shelter have now?
The shelter started with 12 / 2 = 6 cats. The cats they took in increased the number to 12 + 6 = 18 cats. Three cats were adopted, so they had 18 - 3 = 15 cats. One cat had 5 kittens, which increased the number of cats to 15 + 5 = 20 cats. The pet owner came to get his missing cat, so they now have 20 - 1 = 19 cats.
The final answer: 19.