9又2分之1*3.8+5又2分之1*9.5+1/19分之2
=9.5*3.8+5.5*9.5+9.5
=9.5*(3.8+5.5+1)
=9.5*10.3
=(10-0.5)*10.3
=10*10.3-0.5*10.3
=103-5.15
=97.85