Hongqi Children's Wear Factory plans to produce 3,500 sets of children's wear and put them on the market. The first sewing team produces 65 sets a day, and the second sewing team produces 80 sets a day. The two teams produced a total of 20 days. How many sets are left?
红旗童装厂计划生产3500套童装投放市场，第一缝纫小组每天生产65套，第二缝纫小组每天生产80套，两个小组共生产了20天，还剩下多少套没有生产？
<gadget id="calculator">65 + 80</gadget>
<output>145</output>

<gadget id="calculator">145 * 20</gadget>
<output>2_900</output>

<gadget id="calculator">3_500 - 2_900</gadget>
<output>600</output>

<result>600</result>