There are 230 buttons, 42 coats are buttoned, and each coat has 5 buttons, how many buttons are left?
有230颗扣子，给42件上衣钉扣子，每件上衣钉5颗，还剩多少颗扣子？
<gadget id="calculator">5 * 42</gadget>
<output>210</output>

<gadget id="calculator">230 - 210</gadget>
<output>20</output>

<result>20</result>