Respuesta :
you are looking for a unit rate (for 1 quart of red, how much white is used).
notice all red amounts are less than white, so b and c make no sense.
I look at the 4:20 and think, half of the paint would be 2:10, half of that is 1:5
(you could also start with 4:20 and divide each by 4 to get this answer)