The cement plant plans to produce 640 tons of cement in 12 days, half of which was completed in the first 5 days, and the remaining tasks are planned to be completed 3 days ahead of schedule. How many tons should be produced on average per day?
水泥厂计划12天生产水泥640吨，前5天完成了一半，余下的任务打算提前3天完成，剩下的平均每天应生产多少吨？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">12 - 3 - 5</gadget>
<output>4</output>

<gadget id="calculator">(1/2) / 4</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">640 * (1/8)</gadget>
<output>80</output>

<result>80</result>