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

### Instruction:
James buys 3 packs of candy.  He pays with a $20 bill and gets $11 change.  How much did each pack of candy cost?

### Response:
 ลูกอมราคา 20-11= $<<20-11=9>>9
ดังนั้นเขาจ่าย 9/3= $<<9/3=3>>3 ต่อแพ็คละกี่ดอลลาร์