((1又三分之二乘以二加2.5）除以八分之七减二又五分之一)除以1.6
=(5/3*2+5/2)/(7/8-11/5)/(8/5)
=(20/6+15/6)/(35/40-88/40)*(5/8)
=(35/6)/(-53/40)*(5/8)
=-875/318