This year, the son is 6 years old, the father is 36 years old, and the mother is 31 years old. How many years later, the sum of the ages of the parents is 7 times that of the son.
今年儿子6岁，父亲36岁，母亲31岁，多少年后，父母亲年龄之和是儿子的7倍．
<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">31 - 42</gadget>
<output>-11</output>

<gadget id="calculator">36 + (-11)</gadget>
<output>25</output>

<gadget id="calculator">7 - 1 - 1</gadget>
<output>5</output>

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

<result>5</result>