The shop sells a kind of schoolbag. If the price of each schoolbag is 150, then 60% of the selling price is the purchase price, and 40% of the selling price is the money earned. Now there are promotional activities to ensure that the money earned by a schoolbag is no less than 30 yuan, what kind of discount should be determined? (Solve with ratio)
商店卖一种书包，如果每个售价为150，那么售价的60%是进价，售价的40%就是赚的钱，现在要搞促销活动，为保证一个书包赚的钱不少于30元，应该确定怎样折扣？(用比例解决)
<result>8</result>