From the diagram above
mixtures of 3 cups of red paints and 2 cups of green paints for 1 batch
this means for every one batch of brown paint
you have 3 cups of red paints and 2 cups of green paints
for three batches
3 red cups + 3 red cups + 3 red cups = 9 reds cup
2 green cups + 2 green cups + 2 green cups = 6 greens cup
to produce three batches you will need the mixture of 9 red cups of paints and 6 green cups of paint
adding to the diagram you will have 6 more red cups and 4 more green cups