Xiaolan reads a story book. Before dinner, the number of pages she has read is unread (1/5). After dinner, she reads another 6 pages. At this time, the number of pages she has read is unread (1/4) , how many pages does this book have?
小兰看一本故事书，吃晚饭前，已看的页数是未看的(1/5)，晚饭后她又看了6页，这时已看的是未看的(1/4)，这本书有多少页？
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + 5</gadget>
<output>6</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/5) - (1/6)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">6 / (1/30)</gadget>
<output>180</output>

<result>180</result>