The Nevada Supreme Court on Thursday added one more puzzle piece to the list of issues facing the 2013 Legislature when it convenes Monday.In a unanimous decision, the court reversed a district court order invalidating the teachers’ union’s business tax initiative. That sends the 2 percent tax on all businesses earning more than $1 million a year to the legislature. If lawmakers don’t pass it in 40 days, the proposed tax statute goes on the 2014 general election ballot for voters to decide. Teachers say if that happens, they expect a strong majority of Nevadans would support the tax.The tax …