Teacher Wang bought two books. The price of "Mathematics Teaching Handbook" is 21.65 yuan, and the price of "Mathematics Teaching Handbook" is 3.87 yuan cheaper than "Mathematics Teaching Handbook". How much should Mr. Wang pay for these two books?
王老师买了两本书，《数学教学手册》的价钱是21.65元，《数学教学漫谈》的价钱比《数学教学手册》便宜3.87元．王老师买这两本书应付多少钱？
<gadget id="calculator">21.65 - 3.87</gadget>
<output>17.78</output>

<gadget id="calculator">21.65 + 17.78</gadget>
<output>39.43</output>

<result>39.43</result>