A dry cleaning machine loses 2% liquid each time. Help with a relationship between times washed and dye remain?

A machine loses 2 per cent of its dry cleaning liquid each wash. When new, it has 1000 mL of liquid. If it loses 2% each time, how much is left after N washes. Show that after 20 washes it has about 2 thirds of the original liquid. I really need the relationship between N washes and A amount of liquid left. HELP!!!