Answer:
47.91 units²
Explanation:
This can be solved using Heron's triangle (see attached)
in this case, your lengths are
a = 3+9=12
b=3+5=8
c=5+9=14
Hence,.
S = (1/2) x (a + b + c) = (1/2) (12+8+14) = 17
(s - a) = 17 -12 = 5
(s - b) = 9
(s - c) = 3
Area = √ [ s (s-a) (s-b) (s-c) ]
= √ [ 17 x 5 x 9 x 3 ] = √2295 = 47.9061 = 47.91 units² (rounded to nearest hundreth)