Mass box A = 10 grams; mass box B = 5 grams; Mass box C - made of one A and one B. How many boxes of A would be required to make 30 grams of C

Consider a culture medium on which only gram-positive organisms such as staphylococcus aureus colonies can grow due to an elevated nacl level. a yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the ph as a result and changing the color of a ph indicator chemical. this type of medium would be referred to as a differential and enrichment culture.