1)(13 3/4+9 1/6)*1 2/10/(10 3/10-8 1/2)*5/9=
=22 11/12*1 2/10/1 8/10*5/9 =
=143/12*12/10/18/10*5/9=
=143/10/1=143/10
2)(6 8/10-3 3/5)*5 5/6/(3 2/3-3 1/6)*56=
=3 2/10*5 5/6/3/6*56=
=32/10*35/6/28=
=16/2*7/3/28=
=56/3*1/28=2/3
3)143/10 +2/3=429/30+20/30=449/30
4)449/30-27 1/6=
=120 29/30-27 1/6=120 29/30-27 5/30=
=93 2/30=93 1/15