Xiaodong is 12 years old this year, and his father's age is 9 years younger than Xiaodong's four times. How old is dad this year?
小东今年12岁，爸爸的年龄比小东的4倍少9岁．爸爸今年多少岁．
<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<gadget id="calculator">48 - 9</gadget>
<output>39</output>

<result>39</result>