Xiao Ming wants to paint a box of white cloth strips into ribbons, among which (8/20) is painted red, (9/20) is painted blue, what fraction is left?
小明要把一箱白布条涂成彩带，其中(8/20)涂成红色，(9/20)涂成蓝色，剩下几分之几？
<gadget id="calculator">8 / 20</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">9 / 20</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(2/5) + (9/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>