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

### Instruction:
A laboratory has 22 beakers of liquid in a fume hood, and 8 of the beakers have copper ions in them. Adding three drops of a solution will turn the liquid in a beaker blue if there are copper ions present. If the beakers are tested one by one for copper ions and 45 drops are used before all 8 beakers with copper ions are found, how many beakers without copper ions were tested?

### Response:
 มีถ้วยที่ทดสอบไปทั้งหมด 45 / 3 = <<45/3=15>>15 ถ้วยเพื่อหาถ้วยที่มีไอออนทองแดงทั้งหมด
ดังนั้น ทดสอบถ้วยที่ไม่มีไอออนทองแดงไปทั้งหมด 15 - 8 = <<15-8=7>>7 ถ้วย.