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

### Instruction:
 Umri wa Sarah ni sawa na mara tatu umri wa Mark minus 4. Mark ni miaka minne mkubwa kuliko Billy. Billy ni nusu ya umri wa Ana. Ikiwa Ana atakuwa na miaka 15 baada ya miaka 3, Sarah ana umri gani?


### Response:
 Tuseme Sarah ana umri wa x miaka.
Mark ni x/3-4 = <<x/3-4=x/3-4>>x/3-4 miaka
Billy ni x/3-4-4 = <<x/3-4-4=x/3-8>>x/3-8 miaka
Ana ni x/3-8-4 = <<x/3-8-4=x/3-12>>x/3-12 miaka
Baada ya miaka 3, Ana atakuwa na miaka 15 = x/3-12 + 3 = <<x/3-12+3=x/3-9>>x/3-9 miaka
Ikiwa x/3-9 = 15, basi 15*3-9 = <<15*3-9=42>>42 = x
Sarah ana miaka 42