Ali had a collection of seashells. He started with 180 seashells. He then gave away 40 seashells to his friends. He also gave 30 seashells to his brothers. If he sold half of the remaining seashells, how many seashells did he have left? Let's think first. Chain of thought:
When he gave 40 seashells to his friends, Ali had 180 - 40 = 140 seashells. When he gave another 30 seashells to his brothers, he had 140 - 30 = 110 seashells. He also sold half of the seashells, a total of 1 / 2 * 110 = 55 seashells. He was left with 110 - 55 = 55 seashells.
Therefore, the answer is 55.