Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 一个居民协会决定在每条街上种一棵树。这个社区有十八条街。协会希望每隔一棵树是一棵果树，并且他们同意种植相同数量的李子树、梨树和杏树。他们将种植多少种树？


### Response:
 每隔一棵树是一半的树，所以将种植 18 / 2 = <<18/2=9>>9 棵果树。
协会将种植三种果树，所以他们将种植 9 / 3 = <<9/3=3>>3 棵每种树。