A typist typed a manuscript. He typed 30 pages on the first day and 50 pages on the second day, and left 3/7 of the total pages untyped. How many pages does this manuscript have?
一个打字员打一份稿件，第一天打了30页，第二天打了50页，还剩下总页数的(3/7)没有打，这份稿件有多少页？
<gadget id="calculator">30 + 50</gadget>
<output>80</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

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

<result>140</result>