1. 限时计算13+9 = 42-18 = 15-8 = 34-9 =21+19 = 20-13 =36-12 = 31-15 =19+22 = 19+17-16 =24-15 = 14-9+6 =12+16 = 24-8-4 =22+18 = 33-15+7 = 18+17 = 17-12+13 =24+16 = 28-12+14=2. 头脑风暴话说有一天，光头强老师来到教室，发现到了的学生只占了教室此时人数的一半，老师气坏了.请问，究竟来了多少名学生呢？