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

### Instruction:
 费利克斯在他的后院砍树。每砍倒13棵树，他就需要磨一次斧头。磨一次斧头花费他5美元。如果他在磨斧头上花费了35美元，他至少砍倒了多少棵树？


### Response:
 他磨了7次斧头，因为35 / 5 = <<35/5=7>>7
他砍倒了91棵树，因为7 x 13 = <<7*13=91>>91