Susan has been told she needs to take 3 grams of a drug every day. Her pills only come in 250 milligram sizes. How many pills should she take every day?

Susan should take 12 a day Four in the morning, four by lunch and, four by night

Explanation:

3 grams = 3000 milligrams

so 250 milligram pills that's one quarter of 1000.

so four to 1000 then 12 to 3000

Answer;
According to the trichromatic theory of color vision, people who have red-green color blindness have normal blue-sensitive cones, but their other cones are either red-sensitive or green-sensitive. therefore, red and green look the same to them

Explanation; 
According to the trichromatic theory of color vision, there are three varieties of cones. Each type of cone is especially sensitive to certain wavelengths;- red light, green light and blue light. Thus, a given cone will be very sensitive to one of the three colors and only slightly responsive to the other two.
This theory provides a good explanation for the most common form of color blindness; that is red-green color blindness. People with red-green color blindness cannot discriminate between red and green. This is because they have normal blue-sensitive cones, but their other cones are either red-sensitive or green-sensitive.