The number k and 1.4 are additive inverses. drag and drop 1.4 and k to their correct positions on the number line. drag and drop the label “sum” to the sum of 1.4 and k.

For this case we have the following definition:
 The additive inverse of a number is the opposite of that number, that is, the additive inverse of a number x is - x. The sum of a number and its additive inverse is equal to zero.
 We have then: 
 
 From here, we clear the value of k.
 
 Then, we place the values on the number line.
 
 See attached image.

The answer is: a = about 63.59ft2 for 15

Google it that might work