Mingming and his 3 good friends made 7 flowers each, and gave 9 flowers to the children. How many flowers are left?
明明和他的3个好朋友每人做了7朵花，送给小朋友9朵，还剩多少朵．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">28 - 9</gadget>
<output>19</output>

<result>19</result>