The school carried out water-saving activities. A total of 8.4 tons of water was saved in the first 4 days of a certain week, and an average of 4.9 tons of water was saved per day in the last 3 days. How many tons of water was saved on average this week?
学校开展节水活动，某星期前4天共节水8.4吨，后3天平均每天节水4.9吨，这一星期平均每天节水多少吨？
<gadget id="calculator">4.9 * 3</gadget>
<output>14.7</output>

<gadget id="calculator">8.4 + 14.7</gadget>
<output>23.1</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">23.1 / 7</gadget>
<output>3.3</output>

<result>3.3</result>