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

### Instruction:
There were 50 racers in a bicycle charity race at the beginning of the race. After 20 minutes, 30 more racers joined the race. The total number of racers doubled after another 30 minutes. If at the end of the race only 130 people finished the race, what's the total number of people who dropped before finishing the race?

### Response:
 Baada ya dakika 20, kulikuwa na washindani 50+30 = <<50+30=80>>80.
Baada ya dakika nyingine 30, idadi ya washindani iliongezeka mara mbili, jumla ya washindani ni 80*2 = <<80*2=160>>160.
Ikiwa idadi ya washindani waliofika mwisho ni 130, basi washindani 160-130 = <<160-130=30>>30 waliacha kabla ya kumaliza mbio.