Xiangyang Primary School launched reading activities. The fourth grade read 150 books, the fifth grade read 70 more books than the fourth grade, and the sixth grade read three times as much as the fifth grade. How many books did the sixth grade students of Xiangyang Primary School read?
向阳小学开展读书活动．四年级读150本，五年级比四年级多读70本，六年级读的本数是五年级的3倍，向阳小学六年级的学生读了多少本书．
<gadget id="calculator">150 + 70</gadget>
<output>220</output>

<gadget id="calculator">220 * 3</gadget>
<output>660</output>

<result>660</result>