Mathematics problem Li Bai plays with a pot of wine, and when he meets a shop, he doubles it. When he met a flower, he met the shop and the flower three times and asked for the original wine.

This is a folk math problem. The meaning of the question is: Li Bai is walking in the street, drinking with a hip flask. Every time he meets a hotel, the capacity in the hip flask doubles, and every time he meets flowers, he drinks a barrel (barrel is an ancient unit of capacity, 1 barrel = 10 liter). In this way, he met the flowers three times in the shop and finished the wine. How much wine is there in the hip flask?

This problem is solved by an equation. Suppose there are x barrels of wine in the pot. If [(2x-1) × 2-1]× 2-1= 0, the solution is x = 7/8.