First of all substitute a, b and c in
and then i'll show you below
(2^4/5^4)/(-1^3/3^3)x(3^4/5^4)
you can eliminate 5^4 from top and bottom as the cancel out
you then also eliminate 3^3 and the 3^4 becomes 3^1
multiply the rest of them together and you get 2^4/-3
and then it becomes 2^4 x -3^-1
since (1/-3) = -3^-1
the answer would be -16/3 but because you have to express it in index notation therefore its 2^4 x -3^-1