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

### Instruction:
Jasmine and her older sister Alexa went to the store to buy shoes. Alexa's shoes are twice as big as Jasmine's shoes. If Jasmine's shoe size is 7, what's the combined shoe size for both of them?

### Response:
 Ikiwa viatu vya Alexa ni mara mbili ya vya Jasmine, basi ukubwa wake wa viatu ni 7 * 2 = <<7*2=14>>14
Ukubwa wa viatu vyote ni 14 + 7 = <<14+7=21>>21