Answer :
A^2+B^2=C^2
(8)^2+(15)^2=C^2
64+225=C^2
289=C^2
17=C
The length of the third side is 17
Hope this helped (: Good luck!
(8)^2+(15)^2=C^2
64+225=C^2
289=C^2
17=C
The length of the third side is 17
Hope this helped (: Good luck!