2分之3×[1÷（2又10分之1-2.05）＋5分之2]
=3/2*(1/0.05+0.4)
=3/2*(20.4)
=30.6
（6.25＋79×6.25）÷0.5
=(6.25/0.5)(1+79)
=6.25*80/0.5
=12.5*80
=1000