A pet store owner had 12 birds, 9 puppies, 5 cats, and 15 spiders. Half the birds were sold and 3 puppies were adopted. Then, someone left the spider enclosure open and 7 of them went loose. How many animals does the pet store owner have left? Think carefully first, then make a decision:
There are 12 / 2 = 6 birds left. There are 9 - 3 = 6 puppies left. There are 15 - 7 = 8 spiders left. The pet store owner has 5 + 6 + 6 + 8 = 25 animals left. So, the answer is 25.