The A.I. start-up’s valuation tripled in less than 10 months. : OpenAI has completed a deal that values the San Francisco artificial intelligence company at $80 billion or more, nearly tripling its valuation in less than 10 months, according to three people with knowledge of the deal. The company would sell existing shares in a so-called tender offer led by the venture firm Thrive Capital, the people said. The deal lets employees cash out their shares in the company, rather than a traditional funding round that would raise money for business operations.