Mathematical problems of inequality group The price and quantity of goods bought by the two stores are the same. Store a: after purchasing 200 yuan goods, you can apply for a 20% discount card, and later you can enjoy a 20% discount when purchasing goods; store B can apply for a 10% discount card when purchasing 100 yuan goods, and later you can enjoy a 10% discount when purchasing goods At the beginning, we need to use the system of inequalities to solve the problem, not to discuss it by classification,

Mathematical problems of inequality group The price and quantity of goods bought by the two stores are the same. Store a: after purchasing 200 yuan goods, you can apply for a 20% discount card, and later you can enjoy a 20% discount when purchasing goods; store B can apply for a 10% discount card when purchasing 100 yuan goods, and later you can enjoy a 10% discount when purchasing goods At the beginning, we need to use the system of inequalities to solve the problem, not to discuss it by classification,

Let's buy the commodity of X yuan a: 200 + (X-200) * 80% = 0.8x + 40 B: 100 + (X-100) * 90% = 0.9x + 10 when a = B: 0.8x + 40 = 0.9x + 10, then we can calculate x = 300 when a > b: x < 300 when a < B: x > 300, so when you spend 300 yuan, you can spend more than 300 yuan to go to a for shopping