Teacher Sun wants to buy some stationery with RMB 80. He first bought 5 photo albums for RMB 47.5, and then used the remaining money to buy pens. Each pen is RMB 2.5. How many pens can he buy?
孙老师要用80元人民币买一些文具，他先花47.5元买了5本相册，用剩下的钱买钢笔，每支钢笔2.5元，可买几支钢笔？
<result>8</result>