A certain school participated in the elementary school "Hope Cup" mathematics competition, and 12 students won the first prize. There are more second prizes than first prizes (2/3), and third prizes (5/7). How many third prizes are there?
某校参加小学"希望杯"数学竞赛，有12人获一等奖．二等奖人数比一等奖多(2/3)，又是三等奖的(5/7)，获三等奖的有多少．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 + (2/3)</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/3) / (5/7)</gadget>
<output>7/3 = around 2.333333</output>

<gadget id="calculator">12 * (7/3)</gadget>
<output>28</output>

<result>28</result>