А) (6-2 1/10*2 1/7)*4/15 = (6/1-21/10*15/7)*4/15 = (6/1-315/70)*4/15 = (6/1-9/2)*4/15 = (12/2-9/2)*4/15 = 3/2*4/15=12/30=2/5
б) (2 2/3-2 2/9)*(2-1 1/2) = (8/3-20/9)*(2/1-3/2) = (24/9-20/9)*(4/2-3/2) = 4/9*1/2=4/18=2/9
в) (3 3/11*1 2/9-2 3/8)*16/39 = (36/11*11/9-19/8)*16/39 = (396/99-19/8)*16/39 = 117/72*16/39 = 1872/2808=2/3
г) (9/16+4 2/3*9/56)*1 1/7 = (9/16+14/3*9/56)*8/7 = (9/16+126/168)*8/7 = (9/16+3/4)*8/7 = (9/16+12/16)*8/7 = 21/16*8/7 = 168/112=3/2=1 1/2