Read a 280-page book, read (1/4) of the whole book on the first day, and (2/7) of the whole book on the second day, how many pages should you read on the third day?
看一本280页的书，第一天看了全书的(1/4)，第二天看了全书的(2/7)，第三天从多少页看起？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(1/4) + (2/7)</gadget>
<output>15/28 = around 0.535714</output>

<gadget id="calculator">280 * (15/28)</gadget>
<output>150</output>

<gadget id="calculator">150 + 1</gadget>
<output>151</output>

<result>151</result>