The first term is (9x)^3, so the coefficient of x is 9. Since the degree is 3, the second term must have a multiplier of (3 choose 1). 1458 / (3 choose 1) = 486.
486 / (9^2) = 6. Therefore, the coefficient of y must be 6. Since the second term is negative, the coefficient of y is also negative. Thus, this can be written as (9x-6y)^3. Solving for the xy^2 term gives us (3 choose 2) * 9 * 6^2 = or the third option.