题目

Hundreds of years ago, life was much harder than it is today．People didn’t have modern machines．There was no modern medicine, either． Life today has brought new problems．One of the biggest is pollution． Water pollution has made our rivers and lakes dirty． It kills our fish and polluted our drinking water． Noise pollution makes us talk louder and become angry more easily．Air pollution is the most serious kind of pollution．It’s bad for all the living things in the world． Cars, planes and factories all polluted air so thick that it is like a quilt （被子）over a city15．六（3）班的学生有40多人，如果站成人数相等的6行还多3人，如果要战成人数相等的7行还差4人．六（3）班共有学生多少人？