The unit price of the clock is 18 yuan, and the unit price of the desk lamp is 25 yuan. Xiaohua paid 50 yuan and bought a clock and a desk lamp. How much yuan should I get back?
钟的单价是18元，台灯的单价是25元，小华付出50元，买了一个钟和一盏台灯，应找回多少元？
<gadget id="calculator">50 - 18 - 25</gadget>
<output>7</output>

<result>7</result>