Answer:
You will use 2 cups of blue paint for 4 cups of yellow paint.
Step-by-step explanation:
Given that:
There is 1/3 cup of blue paint for every 2/3 cup of yellow paint
We will find unit rate in terms of yellow paint.
2/3 cups of yellow paint = 1/3 cup of blue paint
Multiplying both sides by 3/2

Now,
4 cups of yellow paint =
cups of blue paint
4 cups of yellow paint = 2 cups of blue paint
Hence,
You will use 2 cups of blue paint for 4 cups of yellow paint.