Xiaohua reads a storybook, and reads an average of 39 pages a day, and finishes it in 4 days. If you read 25 pages a day in the first two days, how many pages will you read on average in the next two days?
小华看一本故事书，平均每天看39页，4天看完．若前两天每天看25页，后两天平均每天看多少页？
<gadget id="calculator">39 * 4</gadget>
<output>156</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<gadget id="calculator">156 - 50</gadget>
<output>106</output>

<gadget id="calculator">106 / 2</gadget>
<output>53</output>

<result>53</result>