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

### Instruction:
Lizzy's school choir has a mixture of 80 blonde and black-haired girls. Their teacher decides to add 10 more girls to the choir, who turns out to be blonde. If there were 30 blonde-haired girls in the choir initially, how many black-haired girls are present?

### Response:
 Jumla ya wasichana kwenye kwaya ni 80, na kulikuwa na wasichana 30 wenye nywele za kahawia kwenye kwaya mwanzoni, maana yake kuna wasichana 80-30 = <<80-30=50>>50 wenye nywele za kijivu.
Mwalimu anaongeza wasichana 10 zaidi kwenye kwaya, hivyo kuongeza idadi ya jumla hadi 80+10 = 90 wasichana.
Idadi ya wasichana wenye nywele za kahawia kwenye kwaya sasa ni 30+10 = <<30+10=40>>40 wasichana wenye nywele za kahawia.
Kutoka kwenye idadi ya jumla, idadi ya wasichana wenye nywele za kijivu ni 90-40 = <<90-40=50>>50 wasichana wenye nywele za kijivu.