You can put this solution on YOUR website! Percent means per 100 (cent meaning 100) and is represented by %.
For example 50% of "X" means (50/100)of X. This means X/2.
So to find out what % of 400 is 0.8 , use the formula :
(X/100)multiplied by 400 = 0.8
where X becomes your percent value.
So in this case, X is equal to 0.2
Hope that answered your question !!