Xiao Ming is 12 years old this year, and his grandfather is 4 years younger than 6 times his age. What is the age of his grandfather this year?
小明今年12岁，爷爷的年龄比他的6倍少4岁，爷爷今年的年龄是多少岁．
<gadget id="calculator">12 * 6</gadget>
<output>72</output>

<gadget id="calculator">72 - 4</gadget>
<output>68</output>

<result>68</result>