There are a total of 18 coins of 5 cents and 1 cent in Xiao Ming's piggy bank, totaling 5 yuan. Then how many 5 jiao coins are there?
小明的存钱罐里有5角和1角的硬币共18枚，一共有5元．则5角的硬币有多少枚．
<gadget id="calculator">0.1 * 18</gadget>
<output>1.8</output>

<gadget id="calculator">5 - 1.8</gadget>
<output>3.2</output>

<gadget id="calculator">0.5 - 0.1</gadget>
<output>0.4</output>

<gadget id="calculator">3.2 / 0.4</gadget>
<output>8</output>

<result>8</result>