This year, the mother is 38 years old, and the son is 10 years old. How many years ago, the age of the mother was 5 times that of the son.
今年母亲38岁，儿子10岁，多少年前母亲的年龄是儿子的5倍．
<gadget id="calculator">38 - 10</gadget>
<output>28</output>

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

<gadget id="calculator">28 / 4</gadget>
<output>7</output>

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

<result>3</result>