There are 40 students in the 6th  grade.  25% of them wear glasses and 40% of them wear contact lenses.  How many students do not wear any vision assistance wear?
There are 40 x 25% = 
<gadget id="calculator">40*25*.01</gadget>
<output>10</output>
10 students who wear glasses.
There are 40 x 40% = 
<gadget id="calculator">40*40*.01</gadget>
<output>16</output>
16 students who wear contact lenses.
There are 10 + 16 = 
<gadget id="calculator">10+16</gadget>
<output>26</output>
26 students who wear vision assistance.
There are 40 - 26 = 
<gadget id="calculator">40-26</gadget>
<output>14</output>
14 students who do not wear any vision assistance wear.

<result>14</result>