Question 764357
If one liter covers 15m^2, there is no way to get whole liters to cover 445.5m^2. The ratio is 29.7L. So let's forget that so called requirement. 
This is a problem in which we use the Nicole "n". So called after one of my students, Nicole.
We simply start with the ratio 5:4:2 and multiply each ratio by a constant "n" and get
(1) 5*n:4*n:2*n, wherein the ratios have not changed because n is a constant.
Now we can add the number of liters of the three colors and equate it to the total amount of paint required or
(2) 5*n + 4*n + 2*n = 445.5/15 or
(3) 11*n = 29.7 or
(4) n = 29.7/11 or
(5) n = 2.7
For each color we need the following number of liters;
a) Gold = 5*n or 5*2.7 or 13.5L
b) Blue = 4*n or 4*2.7 or 10.8L
c) Red  = 2*n or 2*2.7 or  5.4L
Add them up and get 29.7L, which will cover 15*29.7 or 445,5m^2
Answer is given by a, b, and c above.
Note that the ratio 13.5:10.8:5.4 is the same as 5:4:2, thanks to Nicole!