1) 21 4/15 + 1 5/6 = 21 8/30 + 1 25/30 = 22 33/30
2) 22 33/30 - 9 7/30 = 13 26/30
3) 13 26/30 + 16 7/24 = ( 13 + 16 ) + ( 26/30 + 7/24 ) = 29 + 13/15 + 7/24 = 29 + 104+35/120 = 29 + 139/120 = 29 + 1 19/120 = 30 19/120
