Given:
3/4 cup of warm water for each batch.
8 batches to be made.
1 cup measuring cup.
3/4 * 8 = (3*8)/4 = 24/4 = 6
She can use 6 cups of water for the 8 batches of paint.
She should make the whole 8 batches as one mixture so that the 6 cups of warm water will be evenly distributed.