Xiao Ming reads a story book, the ones he has read before dinner are unread (1/5), and after dinner he reads another 6 pages, and the ones he has read are unread (1/4). How many pages are there.
小明看一本故事书，吃晚饭前已看的是未看的(1/5)，晚饭后他又看了6页，这时已看的是未看的(1/4)，这本书共有多少页．
<gadget id="calculator">1 + 5</gadget>
<output>6</output>

<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 / 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>