The food factory uses trucks to transport flour, 8 trucks for the first shipment, and 11 trucks for the second time, with an average of 4 tons of flour per truck. After some flour is used up, there are still 4 tons left. How many tons of flour are used?
食品厂用汽车运面粉，第一次运8车，第二次运11车，平均每车装面粉4吨，用去一些面粉后，还剩下4吨．用去面粉多少吨？
<gadget id="calculator">8 + 11</gadget>
<output>19</output>

<gadget id="calculator">4 * 19</gadget>
<output>76</output>

<gadget id="calculator">76 - 4</gadget>
<output>72</output>

<result>72</result>