Xiaoling got 15 questions, 13 questions, and 17 questions correct in three oral calculations, and how many questions she got right each time on average.
小玲3次口算分别算对了15题、13题、17题，平均每次算对了多少题．
<gadget id="calculator">15 + 13 + 17</gadget>
<output>45</output>

<gadget id="calculator">45 / 3</gadget>
<output>15</output>

<result>15</result>