(31/2-21/6):23/5-2/3*21/4+51/6=

1) 31/2-21/6 =144/122)144/12*5/23=720/276=180/69=60/233)2/3*21/4=42/12=21/6=7/24) 60/23-7/2= - 41/465) - 41/46+51/6=2100/276=350/46=175/23