Each sapling is 18 yuan, buy 5 saplings and get one free. Mr. Wang bought 5 trees at a time. How much is each cheaper?
每棵树苗18元，买5个树苗送一棵．王先生一次买了5棵．每棵便宜多少元？
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">18 * (5/6)</gadget>
<output>15</output>

<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<result>3</result>