The area of a triangle in determined by the formula:
[tex] \frac{b \times h}{2} [/tex]
where b is the base of the triangle and h is it's height
You just have to replace the b and h with their values in the formula (b=9.9ft and h=5.5ft)
[tex] \frac{b \times h}{2} = \frac{9.9 \times 5.5}{2} =27.225[/tex]
The answer is 27.225 ft^2