51又2/3*3/5+41又1/3*3/4+31又1/2*2/3=(51+2/3)*3/5+(41+1/3)*3/4+(31+1/2)*2/3=(153/3+2/3)*3/5+(123/3+1/3)*3/4+(62/2+1/2)*2/3=155/3*3/5+124/3*3/4+63/2*2/3=31+31+21=83