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

### Instruction:
Mark and Peter dug ponds in their backyards. Mark’s pond is 4 feet deeper than 3 times Peter’s pond. If Mark’s pond is 19 feet deep, what is the depth of Peter’s pond?

### Response:
 เราจะใช้ p แทนจำนวนฟุตในบ่อของมาร์ค
3*p+4=19
3*p=19-4=15
3p=15
p=<<5=5>>5