Xiao Ming is 10 years old this year, his grandfather is 7 times younger than him and 4 years old, how old is his grandfather this year?
小明今年10岁，爷爷的年龄是他的7倍少4岁，爷爷今年多少岁．
<gadget id="calculator">7 * 10</gadget>
<output>70</output>

<gadget id="calculator">70 - 4</gadget>
<output>66</output>

<result>66</result>