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

### Instruction:
Brennan was researching his school project and had to download files from the internet to his computer to use for reference. After downloading 800 files, he deleted 70% of them because they were not helpful. He downloaded 400 more files but again realized that 3/5 of them were irrelevant. How many valuable files was he left with after deleting the unrelated files he downloaded in the second round?

### Response:
 Alipofuta 70% ya faili za kwanza 800, alijiondoa faili 70/100*800 = <<70/100*800=560>>560.
Alibaki na 800-560 = <<800-560=240>>240 faili muhimu kutoka kwenye upakuaji wa kwanza.
Idadi ya faili alizopakua katika raundi ya pili ilikuwa 400, lakini 3/5*400 = <<3/5*400=240>>240 zao hazikuwa na umuhimu.
Hii inamaanisha kuwa alipakua 400-240 = <<400-240=160>>160 faili muhimu katika raundi ya pili.
Kwa kuandika utafiti wake, Brennan alikuwa na faili muhimu 160+240 = <<160+240=400>>400 za kurejelea kuandika utafiti wake.