There are 20 ballpoint pens in a box, including 5 red ones, 7 blue ones and 8 black ones. If a pen is randomly drawn from it, what is the probability that it is red or black?
盒子里装着20支圆珠笔，其中有5支红色的，7支蓝色的和8支黑色的，从中随意抽出一支笔，抽到的是红色或是黑色的概率是多少？
<gadget id="calculator">5 + 8</gadget>
<output>13</output>

<gadget id="calculator">13 / 20</gadget>
<output>13/20 = around 0.65</output>

<result>13/20 = around 0.65</result>