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

### Instruction:
 Kevin ni muuzaji wa matunda. Daima anauza jumla ya masanduku 50 ya matunda kwa wiki. Wiki iliyopita aliuza masanduku 13 ya zabibu, masanduku 20 ya embe, na yaliyobaki ni mapera. Masanduku mangapi ya mapera aliouza?


### Response:
 Kati ya zabibu na embe, tuna masanduku 13+20 = <<13+20=33>>33.
Masanduku yaliyobaki ni ya mapera, hivyo tuna masanduku 50-33=<<50-33=17>>17 ya mapera.