Huanhuan, Xiaoqiang, and Xiaoyang went swimming in the swimming pool and bought 3 swimming laps. Each lap was 13 yuan. How much did they have to pay?
欢欢、小强、小阳去泳池游泳，买了3个泳圈，泳圈每个13元，他们要付多少钱？
<gadget id="calculator">3 * 13</gadget>
<output>39</output>

<result>39</result>