A circle of radius 4 is inscribed into quadrilateral with 3 known sides 6, 14, 16, what is area of the quadri

What is the area of this quadrilateral?

Take a look at this link here:
http://en.wikipedia.org/wiki/Tangential_…

By the Pitot Theorem, if x is the fourth side of the quadrilateral, then:
6 + 14 = 16 + x ==> x = 4.

The area of the quadrilateral is then:
A = rs, where s is the semi-perimeter
= (4)[(4 + 6 + 14 + 16)/2]
= 80 units^2.

I hope this helps!