2又4/5*23.4+11.1*57.6+6.54*28
=2.8*23.4+11.1*57.6+6.54*28
=28*2.34+11.1*57.6+6.54*28
=28*2.34+6.54*28+11.1*57.6
=28*(2.34+6.54)+11.1*57.6
=28*8.88+11.1*57.6
=2.8*11.1*8+11.1*57.6
=11.1*22.4+11.1*57.6
=11.1*(22.4+57.6)
=11.1*80
=888