Brianna and her brother want to make chocolate chip muffins and blueberry muffins for their school fundraiser. They only have 16 cups of milk and 15 cups of flour. It takes 4 cups of milk and 3 cups of flour to make chocolate chip muffins. It takes 2 cups of milk and 3 cups of flour to make blueberry muffins. Let x represent the number of chocolate chip muffins and y represent the number of blueberry muffins.