Students A, B, C, and D donate books to the school. A and B donate a total of 38 books, and C and D donate a total of 70 books. The average number of books each person donates.
甲、乙、丙、丁四位同学为学校捐图书，甲、乙两人共捐38本，丙、丁两人共捐70本，平均每人捐书多少本．
<gadget id="calculator">38 + 70</gadget>
<output>108</output>

<gadget id="calculator">108 / 4</gadget>
<output>27</output>

<result>27</result>