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

### Instruction:
 迈卡在他的水族箱里有7条鱼。肯尼斯的水族箱里有迈卡的三倍鱼，而马蒂亚斯的水族箱里比肯尼斯少15条鱼。男孩们总共有多少条鱼？


### Response:
 肯尼斯的水族箱里有3 x 7 = <<3*7=21>>21条鱼。
马蒂亚斯的水族箱里有21 - 15 = <<21-15=6>>6条鱼。
男孩们总共有7 + 21 + 6 = <<7+21+6=34>>34条鱼。