(103/4-12: 11/5)*4/9+21/6+31/4: 51/5

(103/4-12:11/5)*4/9+21/6+31/4:51/5=(103/4-12*5/11)*4/9+7/2+31/4*5/51=
=(103/4-60/11)*4/9+7/2+155/204=103/4*4/9-60/11*4/9+7/2+155/204=
=103/9-20/11*4/3+7/2+155/204=103/9-80/33+7/2+155/204=
=11 4/9-2 14/33+3 1/2+155/204=11 44/99-2 42/99+3 102/204+155/204=
=9 2/99+3 257/204=9 2/99+4 53/204=9 136/6732+4  1749/6732=13 1885/6732