We have 600 grams of grass, which has 450 grams of water. This means that there are 600 - 450 = 150 grams of dry weight (aka dry grass without any water)
20% of the dry weight is the amount of protein the rabbit gets
20% of dry weight = 20% of 150 = (20/100)*150 = 0.20*150 = 30
Answer: The rabbit eats 30 grams of protein per day
