Answer:
r = 15
Step-by-step explanation:
I don't really have an explanation, I'm just good at quick math,
I'm sorry if you wanted an explanation, I would explain but I am really bad at explaining math.
Yellow:blue is a ratio of 2:3, meaning that 2/5 of the desired mixture is yellow. From this, you need to find how much yellow is necessary for 20 ounces. Well, 2/5 of the 20 ounces will be yellow paint, while the other 3/5 will be blue. So she will need 8 ounces of yellow paint to get 20 ounces of the desired mixture. Hope this helps! :)