Grandpa is 84 years old this year, 7 times that of Xiao Ming. How old is Xiao Ming and grandpa?
爷爷今年84岁，是小明的7倍．小明和爷爷相差几岁？
<gadget id="calculator">84 / 7</gadget>
<output>12</output>

<gadget id="calculator">84 - 12</gadget>
<output>72</output>

<result>72</result>