The Mavericks (8-16, 5-6 Summit) shot 63 percent from the floor, hit 6 of 12 3-pointers and made 16 of 20 free throws to win their third straight game and avenge an 18-point loss to the Mastadons (10-14, 3-7) on Jan. 5.
The Mavericks trailed 41-36 at halftime but hit 15 of their next 16 shots and finished with a 78.2 shooting percentage in the second half. They were up by two with 7:45 remaining when Simmons hit a 3-pointer, Carter followed with a three-point play and Simmons added a layup to make it 75-65 with 6:34 remaining.
Seton Hall sophomore Isaiah Whitehead will stay in the NBA draft and not return for his junior season.
Washington State's trio of Josh Hawkinson, Conor Clifford and Ike Iroegbu have withdrawn from the NBA draft and will play their senior season with the Cougars.
Gonzaga center Przemek Karnowski, who missed most of last season with a back injury, says he is returning for another year.