The school carried out water-saving activities, saving 14.7 tons of water in the first 3 days of this week, and 2.1 tons of water per day in the last 4 days. How many tons of water is saved on average per day this week?
学校开展节水活动，这个星期的前3天节约水14.7吨，后4天平均每天节约水2.1吨．这个星期平均每天节约水多少吨？
<gadget id="calculator">2.1 * 4</gadget>
<output>8.4</output>

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