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

### Instruction:
Marta works on her grandparent's farm to raise money for a new phone. So far, she has collected $240. For every hour she works, she receives $10. Her grandmother often gives her tips, and she has collected $50 in tips in total. How many hours has Marta worked on the farm so far?

### Response:
 ไม่นับเคล็ดลับ มาร์ตาได้รับเงิน 240 - 50 = 190 ดอลลาร์
190 ดอลลาร์ / 10 ดอลลาร์ต่อชั่วโมง = 19 ชั่วโมง