Yahoo Inc’s plans to turn around its struggling core business are set to dominate its earnings report on Tuesday, with investors keen to see if CEO Marissa Mayer will push ahead with a proposed spin-off or entertain calls for a complete sale. The spin-off of its main business which includes its search engine and digital advertising units was flagged by Mayer in December after Yahoo abandoned efforts to sell its stake in Alibaba Group Holding Ltd, but the company has provided few details.