The original price of towels in the supermarket is 16 yuan per towel. Now buy three and get one free. How much is each towel cheaper?
超市的毛巾原价是16元/条，现在买三送一，每条便宜多少钱？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">16 * (3/4)</gadget>
<output>12</output>

<gadget id="calculator">16 - 12</gadget>
<output>4</output>

<result>4</result>