A gift shop bought a batch of New Year's cards at a price of 10 yuan and 30 pieces, and sold them at a price of 10 yuan, earning a total of 100 yuan. How many New Year's cards did the gift shop sell?
某礼品店以10元30张的价格买进一批贺年卡，又以口元10张价格卖出去，共赚100元．该礼品店卖出多少张贺年卡？
<result>6_700</result>