81/8 дм - 2 1/4 дм= 9ч - 5 1/4 ч = 20 3/8 - (6 - 2 1/6)= 11 7/10 - 5 7/30 - 3 4/15=

65/8дм-9/4дм = 65/8дм-18/8дм=47/8дм = 5 7/8дм
9ч-21/4ч=36/4ч-21/4ч=15/4ч =3 3/4ч
163/8 - (36/6 - 21/6)=163/8 - 15/6=489/24 - 60/24=429/24
11 21/30 - 5 7/30 - 3 8/30=6 14/30 - 3 8/30=3 6/30=3 1/5