Two typists, A and B, typed a manuscript together. On the first day, A typed (1/4) of the total, and B typed (2/5) of the total. As a result, there were still 7000 characters left untyped. How many words are there in this manuscript?
甲乙两名打字员合打一份稿件，第一天甲打了总数的(1/4)，乙打了总数的(2/5)，结果还有7000字没有打．这份稿件共有多少字？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) + (2/5)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">1 - (13/20)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">7_000 / (7/20)</gadget>
<output>20_000</output>

<result>20_000</result>