Xiaohong went to the amusement park with her father and mother to take the electric plane. When buying the ticket, Xiaohong paid 50 yuan and got back 30 yuan. It is known that the fare for children on electric planes is half of the fare for adults, so how much is the fare for children on electric planes?
小红和爸爸、妈妈一起去游乐场乘电动飞机，买票时小红付出50元钱，找回了30元．已知电动飞机的儿童票价是成人票价的一半，那么电动飞机的儿童票价是多少元钱．
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<result>4</result>