Xiao Dingding bought 4 red bean egg tarts at KFC for 30 yuan, and the money he got back was just enough to buy 2 pairs of roasted wings with a unit price of 7 yuan. How much does a red bean egg tart cost?
小丁丁在肯德基用30元买了4个红豆蛋挞，找回的钱正好可以买2对单价为7元的烤翅，一个红豆蛋挞要多少元？
<gadget id="calculator">2 * 2 * 7</gadget>
<output>28</output>

<gadget id="calculator">30 - 28</gadget>
<output>2</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>