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

### Instruction:
The length of the straight part of a river is three times shorter than the crooked part. If the river is 80 miles long, how long is the straight part of the river?

### Response:
 Tuseme urefu wa sehemu moja kwa moja ya mto ni x.
Urefu wa jumla wa mto ni urefu wa sehemu moja kwa moja plus mara tatu ya urefu wa sehemu moja kwa moja kwa sehemu iliyopinda, ambayo ni x+3x = 80
Urefu wa jumla wa mto ni 4x=80
Sehemu moja kwa moja ya mto ni x=80/4 = <<80/4=20>>20 maili.