find the area of quadrilateral ABCD.

Answer:
Step-by-step explanation:
[tex]P_{ABCD}=P_{ACD}+P_{ABD}[/tex]
We can use Heron's formula to calculate area of triangles:
[tex]P_\triangle=\sqrt{s(s-a)(s-b)(s-c)}[/tex] where:
a, b, c - sides of triangle
s - semi-perimetr of triangle {(a+b+c):2}
ΔACD:
a = 4.39 , b = 3.42 , c = 4.57
s = (4.39 + 3.42 + 4.57)÷2 = 12.38÷2 = 6.19
[tex]P_{ACD}=\sqrt{6.19(6.19-4.39)(6.19-3.42)(6.19-4.57)}\\\\P_{ACD}=\sqrt{6.19\cdot1.8\cdot2.77\cdot1.62}=\sqrt{49.9986108}=7.070969579...\\\\P_{ACD}\approx7.071[/tex]
ΔACD:
a = 5.44 , b = 7.84 , c = 3.42
s = (5.44 + 7.84 + 3.42)÷2 = 16.7÷2 = [tex]P_{ACD}=\sqrt{8.35(8.35-5.44)(8.35-7.84)(8.35-3.42)}\\\\P_{ACD}=\sqrt{8.35\cdot2.91\cdot0.51\cdot4,93}=\sqrt{61.09371855}=7.81624708...\\\\P_{ACD}\approx7.816[/tex]
[tex]P_{ABCD}=P_{ACD}+P_{ABD}\\\\P_{ABCD}\approx7.071+7.816 = 14.887\\\\P_{ABCD}\approx 14.89[/tex]