The father is 32 years old this year, and the son is 4 years old. When the sum of the ages of the father and son is 50 years old, how many years should it be?
爸爸今年是32岁，儿子是4岁，当父子俩年龄之和是50岁时，应该是多少年之后的事．
<gadget id="calculator">32 - 4</gadget>
<output>28</output>

<gadget id="calculator">50 + 28</gadget>
<output>78</output>

<gadget id="calculator">78 / 2</gadget>
<output>39</output>

<gadget id="calculator">39 - 32</gadget>
<output>7</output>

<result>7</result>