To do this problem, you will need to know the side lengths of the triangle. If you have those, just plug them in for a, b, and c and evaluate the square root.
Here is an example. If the sides are 3, 4, 5. It would be:
The 6 is in the formula because it is the semi-perimeter (half).
The formula of Heron is given by: =A where s is given by (a+b+c)/2 and A is the area. Here, we have a=11, b=9, c=6. Hence, s=13. Substituting, we get that A=. Thus A^2=728 and A=26.98. This yields that A=27 given the exercise options.
An integer divided by its opposite always equals -1: this is false. Any number which is not 0 divided by it's opposite is in fact equal to -1, but since 0 is also an integer, it's false. You are right, good job!