A typist types a manuscript. I typed 30 pages on the first day, and typed 20 pages more on the second day than on the first day. I typed this manuscript in two days (4/7). How many pages does this manuscript have?
一个打字员打一篇稿件．第一天打了30页，第二天比第一天多打20页，两天共打了这篇稿件的(4/7)．这篇稿件有多少页？
<gadget id="calculator">20 + 30 + 30</gadget>
<output>80</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">80 / (4/7)</gadget>
<output>140</output>

<result>140</result>