（2又9分之2×5分之4+2有9分之2×6.2-5.8×2有9分之2-5分之1÷20分之9）×20分之9
=[(20/9)×(4/5)+(20/9)×6.2-5.8×(20/9)-(1/5)×(20/9)]×(9/20)
=[(20/9)×[(4/5)+6.2-5.8-(1/5)×(20/9)]×(9/20)
=(20/9)×(0.8+6.2-5.8-4/9)×(9/20)
=(20/9)×(9/20)×(1.2-4/9)
=1.2-4/9
=6/5-4/9
=54/45-20/45
=34/45