A forest farm has planted 1,200 hectares of trees this year, of which willow accounts for (3/5). Later, some willows were planted, and at this time willows accounted for (5/7). How many hectares of trees have been planted in this forest farm this year?
一个林场今年已植树1200公顷，其中柳树占(3/5)．后来又植了一部分柳树，这时柳树占(5/7)．今年这个林场共植树多少公顷？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/5) / (2/7)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">1_200 * (7/5)</gadget>
<output>1_680</output>

<result>1_680</result>