There are four numbers 6, 3, 0, and 7. Now a new number needs to be added to increase their average by 1. What is the newly added number?
有四个数是6、3、0、7，现在要添加一个新数，使它们的平均数增加1，新添加的数是多少．
<gadget id="calculator">6 + 3 + 0 + 7</gadget>
<output>16</output>

<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">25 - 16</gadget>
<output>9</output>

<result>9</result>