Question 72422
If I understand your problem correctly, it is:
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{{{12 - sqrt(100) + 9^2}}}
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The square root of 100 is 10 (the number when multiplied by itself results in 100), and 
9 squared is 9 times 9 which is 81.  Substituting these two values simplifies your problem
to:
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{{{12 - 10 + 81}}}
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and this is 2 + 81 = 83
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Hope this helps you understand how to work problems such as these.