University of Maine System trustees are voting on a measure to freeze tuition rates for the upcoming school year at 2012 levels for in-state undergraduates. Trustees are voting Monday at their meeting in Bangor on the system’s operating budget for fiscal year 2014, which begins July 1. As part of the budget vote, trustees will set tuition rates. Tuition was frozen for the 2012-2013 school year at the state’s seven universities, the first time that had happened in 25 years. Trustees on Monday are voting on a proposal to keep them frozen. Next year’s operating budget is about $522 million, which is up about $1 million from this year. The University of Maine System has seven universities and an annual enrollment of nearly 40,000 students.