Teacher Wang took 180 yuan to buy saplings. The original price was 15 yuan per tree. Now the nursery is promoting buy four and get one free. How many saplings can he buy at most?
王老师拿着180元钱去买树苗，原价15元/棵，现在苗圃搞促销活动买四送一，他最多能买多少棵树苗？
<gadget id="calculator">180 / 15</gadget>
<output>12</output>

<gadget id="calculator">180 / 15 / 4</gadget>
<output>3</output>

<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<result>15</result>