Answer
$$K = 83$$
Work Step by Step
1. If we take all the coefficients of the following equation:
$$N_2(g) + 3H_2(g) \leftrightharpoons 2 NH_3(g)$$
And divide them by 3, we get the reaction we have.
Thus, we just need to find the cube root (**1/3) of K for the equation above.
$$K'' = \sqrt [3] {K} = \sqrt [3] {5.8 \times 10^5} = 83$$
