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

### Instruction:
June made a design with 20 equal tiles. Three tiles are yellow and the number of blue tiles is one more than the number of yellow tiles. Six tiles are purple and the remaining tiles are white.  How many white tiles are there?

### Response:
 Kuna vigae 3 + 1 = <<3+1=4>>4 vya buluu.
Jumla ya vigae vya manjano, buluu, na zambarau ni 3 + 4 + 6 = <<3+4+6=13>>13.
Hivyo, vigae 20 - 13 = <<20-13=7>>7 ni vya kijivu.