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

### Instruction:
Sarah's age is equal to three times Mark's age minus 4. Mark is four years older than Billy. Billy is half Ana's age. If Ana will be 15 in 3 years, how old is Sarah?

### Response:
 เซาร่า = 3*มาร์ค-4
มาร์ค = บิลลี่+4
บิลลี่ = อานา/2
อานา = 15
เซาร่า = 3*(บิลลี่+4)-4 = 3*(อานา/2+4)-4 = 3*(15/2+4)-4 = 3*(8+4)-4 = 3*12-4 = 36-4 = <<36-4=32>>32