What is the answer to number 18 and how did you solve it? !

So let's add up all the numbers making sure to line up the decimal points.

   4.98
   0.97
   0.39
+ 2.79

   9.13

Now we subtract 9.13 from 40. NOT 40 from 9.13.

  40.00
-   9.13

  30.87

The correct answer is 30.87. 

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