"a house is built on a triangular plot of land. two sides of the plot are 160 feet long and they meet at an angle of 85 degrees. if a fence is to be built around the property, how much fencing material is needed? "

            C= 85 degrees
                  / \         
                 /    \
a= 160    /        \    b= 160
             /            \
        B /\ A
                   c

What you're looking for is c so you can add a, b, and c together to get the material. To do this you need to use this formula, otherwise known as Law of Cosines:
c^2 = a^2 + b^2 - 2abcosC
c^2 = 25600 + 25600 - (2)(160)(160)(cos85)
c^2 = 51200 - (51200)(cos85)
c^2 = 51200 - (-50400.084)
c^2 = 101600.084
c = 318.749
c + a + b = 638.749 or 639 ft if you're looking for a whole number
Keep in mind this answer is if what you're looking for is the perimeter, please let me know if it's the area you are looking for