When Xiaoqiang was 12 years old, his grandfather was 6 times his age. This year Xiaoqiang was admitted to university, and his grandfather was exactly 4 times his age. How old is he this year?
小强12岁时，爷爷的年龄是他的6倍，今年小强考上大学，他爷爷的年龄正好是他的4倍，爷爷今年多少岁．
<gadget id="calculator">12 * 6</gadget>
<output>72</output>

<gadget id="calculator">72 - 12</gadget>
<output>60</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>