There are 20 spoons of the same model, among which there are 11 first-class spoons, 7 second-class spoons, and 2 third-class spoons. One of them is randomly selected. What is the possibility of not getting the third-class spoon?
有20个型号相同的勺子，其中一等品11个，二等品7个，三等品2个，从中任意取一个，没有取得三等品的可能性是多少
<gadget id="calculator">11 + 7</gadget>
<output>18</output>

<gadget id="calculator">18 / 20</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>