Mom went to the supermarket to buy 3 water bottles, paid the salesperson 100 yuan, and the salesperson got back 10 yuan. What is the average price of each water bottle?
妈妈去超市买了3个水瓶，付给营业员100元，营业员找回了10元，平均每个水瓶售价多少元？
<gadget id="calculator">100 - 10</gadget>
<output>90</output>

<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<result>30</result>