Answer:
k = -3
Step-by-step explanation:
(1/81) = 3^k
Note that 81 is 3^3 [3*3*3 - 81]
So let's rewrite (1/81) as 1/(3^3)
(1/3^3)= 3^k
1/3^3 can then be rewritten as 3^-3
3^-3 = 3^k
Therefore, k = -3
