Dad bought 5 sets of "One Hundred Thousand Whys", paid the salesperson 450 yuan, and got 15 yuan back. How much does each set of "One Hundred Thousand Whys" cost?
爸爸买了5套《十万个为什么》，付给营业员450元钱，找回15元．每套《十万个为什么》要多少钱？
<gadget id="calculator">450 - 15</gadget>
<output>435</output>

<gadget id="calculator">435 / 5</gadget>
<output>87</output>

<result>87</result>