Teacher Zhang brought a sum of money. I originally planned to buy only footballs, but I can buy 18 of them. As a result, the money was used to buy 6 footballs and 20 basketballs. It is known that each basketball is 54 yuan, how much does each football cost?
张老师带了一笔钱．原打算只买足球，正好可以买18只．结果用这笔钱买了6只足球和20只篮球．已知每只篮球54元，每只足球需要多少元？
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">20 / 12</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">54 * (5/3)</gadget>
<output>90</output>

<result>90</result>