小明：m小红：2m-4小华：（2m-4）/2+1Sn=m+2m-4+(2m-4)/2+1=4m-5
m+2m-4+(2m-4)/2+1=4m-5
和是4m-5=m+2m-4+(2m-4)/2+1=4m-5
小明是m，小红为2m-4 ,小华为m-1,总共为4m-5
