=(98-49/50)*1/49+(78-39/40)*1/39+(58-29/30)*1/29
=98*1/49-49/50*1/49+78*1/39-39/40*1/39+58*1/29-29/30*1/29
=2-1/50+2-1/40+2-1/30
=6-47/600
=5又553/600