Answer:
800ml.
Step-by-step explanation:
If 1 litre = 1000 ml, then
[tex]\small\sf{\quad\dfrac{4}{5} \: of \: a \: litre}[/tex]
[tex] : \implies\small\sf{\dfrac{4}{5} \: of \: 1000}[/tex]
[tex] : \implies\small\sf{\dfrac{4}{5} \times 1000}[/tex]
[tex] : \implies\small\sf{\dfrac{4 \times 1000}{2}}[/tex]
[tex] : \implies\small\sf{\cancel{\dfrac{4000}{5}}}[/tex]
[tex] : \implies\small{\sf{800 \: ml}}[/tex]
∴ The answer is 800 ml.