2÷（2又2/9*4/5+2又2/9-1/5*2又2/9）*9/20
=2÷【20/9*（4/5+1-1/5）】*9/20
=2÷【20/9*8/5】*9/20
=2÷32/9*9/20
=2×9/32×9/20
=81/320