The price of a pair of badminton rackets is 78 yuan, and the price of a pair of tennis rackets is 15 yuan more than three times the price of this pair of badminton rackets. How much is the price of a pair of badminton rackets cheaper than the price of a pair of tennis rackets?
一副羽毛球拍的价格是78元，一副网球拍的价格比这副羽毛球拍的价格的3倍还多15元，一副羽毛球拍的价钱比一副网球拍的价钱便宜多少元？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">78 * 2</gadget>
<output>156</output>

<gadget id="calculator">156 + 15</gadget>
<output>171</output>

<result>171</result>