The age of the grandfather this year is 7 times the age of the grandson, and the age of the grandfather 3 years ago is 10 times the age of the grandson, then how many times the age of the grandfather 6 years ago is the age of the grandson.
今年爷爷的年龄是孙子年龄的7倍，3年前爷爷的年龄是孙子年龄的10倍，则6年前爷爷的年龄是孙子年龄的多少倍．
<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">30 - 3</gadget>
<output>27</output>

<gadget id="calculator">10 - 7</gadget>
<output>3</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<gadget id="calculator">7 * 9</gadget>
<output>63</output>

<gadget id="calculator">63 - 6</gadget>
<output>57</output>

<gadget id="calculator">57 / 3</gadget>
<output>19</output>

<result>19</result>