51又1/4*4/5+41又1/3*3/4+31又1/2*2/3 =(50+5/4)*4/5+(40+ 4/3)*3/4 +(30+ 3/2)*2/3 =40 + 1 + 30 +1 + 20 +1=93.2013*2011/2012+1/2012=(2012+ 1)*2011/2012+1/2012=2011 + 2011/2012+1/2012=2011 +1=2012