20% of 50 people think horse #2 will win the big race.  60% of the remaining people think horse #7 will win.  The rest of the people think horse #12 will win the big race.  How many people think that horse #12 will win?
20% of 50 people are pulling for horse #2 so that's .20*50 = 
<gadget id="calculator">.20*50</gadget>
<output>10</output>
10 people
10 out of 50 people think horse #2 will win which leaves 50-10 = 
<gadget id="calculator">50-10</gadget>
<output>40</output>
40 people
60% of 40 people think horse #7 will win so that's .60*40 = 
<gadget id="calculator">60*.01*40</gadget>
<output>24</output>
24 people.
That leaves 40-24 = 
<gadget id="calculator">40-24</gadget>
<output>16</output>
16 people that think horse #12 will win.

<result>16</result>