Answer:
600 ml 
Explanation:
Given,
240 ml of milk provides about 8 grams of protein,
That is, the ratio of grams of protein provided and milk = 

Let x be the quantity of milk in ml that provides 20 grams of protein,
So, the ratio of grams of protein provided and milk = 


By cross multiplication,
8x = 4800
Divide both sides by 8,
x = 
 = 600
Hence, 600 ml milk should be needed to provide 20 grams of protein.