The school prepared 1,500 yuan to buy potted plants to beautify the campus. The unit price of each pot is 15 yuan. If you buy 4 pots at a time, you only need to pay 50 yuan. How many more pots can the school buy?
学校准备了1500元购买盆栽美化校园．每盆的单价是15元，如果一次买4盆只需要付50元，这样学校可以多买几盆？
<gadget id="calculator">50 / 4</gadget>
<output>25/2 = around 12.5</output>

<gadget id="calculator">1_500 / (25/2)</gadget>
<output>120</output>

<gadget id="calculator">1_500 / 15</gadget>
<output>100</output>

<gadget id="calculator">120 - 100</gadget>
<output>20</output>

<result>20</result>