Three good friends strive to do good deeds. One of them has 8 good deeds, the other has twice as many good deeds, and the third has 3 more good deeds than the sum of the first two. Ask them how many good deeds they have done on average.
三个好朋友争做好事，一人做好事8件，另一个是他的2倍，第三个则是前两人所做好事之和还多3件，问三人平均做多少件好事．
<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">8 + 16 + 3</gadget>
<output>27</output>

<gadget id="calculator">8 + 16 + 27</gadget>
<output>51</output>

<gadget id="calculator">51 / 3</gadget>
<output>17</output>

<result>17</result>