5 numbers are written in a row, the average of the first 3 numbers is 15, and the average of the last two numbers is 10, what is the average of these 5 numbers?
5个数写成一排，前3个数的平均数是15，后两个的数的平均数是10，这5个数的平均数是多少．
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">45 + 20</gadget>
<output>65</output>

<gadget id="calculator">65 / 5</gadget>
<output>13</output>

<result>13</result>