Bai Ruozhu stifled a laugh, not because she was mocking the ancients, but because the literati of Danliang Country didn't place much emphasis on arithmetic.
"You said two brushes, one inkstone, and four reams of paper cost thirty-eight taels of silver, and then one brush, one inkstone, and two reams of paper cost eighteen taels of silver. If we double your second condition, meaning two brushes, two inkstones, and four reams of paper, that would be thirty-six taels of silver. Isn't that more than your first condition by one inkstone, yet it still costs two taels less? How would that make sense?" Bai Ruozhu explained with a smile.
Worried that people wouldn't understand, she wrote it out on paper, held it up for everyone to see, and those in the front row immediately understood—it was indeed inconsistent with the earlier conditions, which meant the problem was flawed.