After a visit to the newly opened aquarium, 40 percent of the aquarium visitors fell ill from a mysterious disease. If there were 500 visitors, how many of them did not fall ill?
If there were 500 visitors, and 40% of them fell ill, the number of visitors who fell ill is 40/100*500 = 
<gadget id="calculator">40/100*500</gadget>
<output>200</output>
200 people.
The number of visitors who did not get ill is 500-200 = 
<gadget id="calculator">500-200</gadget>
<output>300</output>
300.

<result>300</result>