Answer
$19.90 \ square \ units $
Work Step by Step
According to Heron's formula, the area of a triangle with sides $a,b$ and $c$ is given by:
$K=\sqrt{s(s-a)(s-b)(s-c)}$; where $s=\dfrac{a+b+c}{2}$
Therefore, $s=\dfrac{5+8+9}{2}=11$
In order to find the area of a triangle we will have to substitute the data into Heron's formula.
$K=\sqrt{11(11-5)(11-8)(11-9)} \approx 19.90 \ square \ units $
