（5.9+0.35)*2.5
=6.25*2.5
=25/4*5/2
=125/8
21/1.5-0.15
=14-0.15
=13.85
3.7*99+3.7
=3.7*99+3.7*1
=3.7*(99+1)
=3.7*100
=370