"Wangwang Snow Cake" is 12 yuan per bag, buy 3 bags and get 1 bag free, buy 3 bags at a time, how much cheaper is each bag
"旺旺雪饼"每袋12元，买3袋送1袋，一次买3袋，每袋可便宜多少元
<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">12 * (3/4)</gadget>
<output>9</output>

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<result>3</result>