piece of clothing needs 2 buttons, and there are 4 pieces of clothing with 12 buttons. After all the buttons are fastened, how many buttons are left?
一件衣服要钉2个扣子，现有4件衣服和12个扣子，把衣服都钉上扣子后，还剩多少个扣子？
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>