1) 5/34*7/9-5/34*4/27=5/34*(7/9-4/27)=5/34*(21/27-4/27)=
=5/34*17/27=5/27*17/34=5/27*1/2=5/54
2) 49/64*8/9+11/32*8/9-3/64*8/9=49/8*1/9+11/4*1/9-3/8*1/9=
=1/9*(49/8+22/8-3/8)=1/9*68/8=1/9*17/2=17/18
3) 11/15*5/26+5/26*2/15=5/26*(11/15+2/15)=5/26*13/15=5/15*13/26=1/3*1/2=1/6