There are 18 grandmothers in the nursing home, with an average age of 75. There are 12 grandpas, the average age is 70 years old. What is the average age of these elderly people?
敬老院有18位老奶奶，平均年龄是75岁．有12位老爷爷，平均年龄是70岁．这些老人的平均年龄是多少岁？
<gadget id="calculator">75 * 18</gadget>
<output>1_350</output>

<gadget id="calculator">70 * 12</gadget>
<output>840</output>

<gadget id="calculator">1_350 + 840</gadget>
<output>2_190</output>

<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">2_190 / 30</gadget>
<output>73</output>

<result>73</result>