how did the elders try to solve the problem juan tomas brought up

You can find this in Chapter 4. Just before Kino goes to town to sell the Pearl, he Juan Tomas discuss what the elders had done to get a fair price for their treasures. They gathered all their pearls together and sent an agent to the city with the pearls. The agent would get a good price, take his service fee and bring the money back. Unfortunately the agent disappeared with the pearls. They tried again and the same thing happened. So, the Elders decided to go back to the old ways and they were much happier. This cautionary tale serves as lesson for Kino and perhaps a little bit of foreshadowing.