There is the same number of boys andgirlson a school bus when it aparts from school.一开始 ,男孩和女孩一样多。At the firststop , 4 boysgetoff the bus and nobody gets on 4个男孩下去了。After the first stop , there are twice as many girls as boys on the bus 女孩是男孩的2倍。最后问多少个女孩在车上。设为a.a/2+4=a
a=8...