Let \\\\(x\\\\) be the number of protons. The number of neutrons is \\\\(\\displaystyle x+0.317x=1.317x\\\\). The mass number is \\\\(81\\\\). It is equal to the sum of the number of protons and the number of neutrons.\\\\(\\displaystyle 81 = x +1.317 x =2.317x \\\\)\\\\(\\displaystyle x = 35 \\\\)Hence, the symbol is \\\\(\\displaystyle _{35}^{81}Br \\\\).