me assume yu meen (4/5)*(3.1)
but if yu want "order av ops", & yu dont suppli the parens, yu du times first
Yu sae "for-fifths av"...that imply yu gotta yuze (4/5) as a yunit
Then yu multipli 0.8 times sumthun
yu sae "three and..." this impli yu gotta kombine 3 with sumthun intu 1 thang
thus yu get 3.1 as 1 thang
yu hav 0.8*3.1=2.48