NEW YORK—Warren Buffett resigned Wednesday as trustee of the Bill and Melinda Gates Foundation, which says it will announce plans in July to answer questions raised about its leadership structure as it deals with the divorce of its two founders. The announcement from Buffett comes weeks after Bill and Melinda Gates revealed that they were divorcing after 27 years of marriage but would continue to jointly run the foundation, one of the largest charitable foundations in the world. Buffett is one of three members of the foundation’s board, the others are Bill and Melinda Gates. “For years I have been a trustee—an inactive trustee at that—of only one recipient of my funds, the Bill and Melinda Gates Foundation (BMG). I am now resigning from that post, just as I have done at all corporate boards other than Berkshire’s,” Buffett said in a prepared statement Wednesday. “The CEO of BMG is …