If the sum of the coefficients in the expansion of (3x-1 / x) ^ n is 128, then the sixth term of the expansion is_____ Knowledge of binomial coefficient in Senior High School

If the sum of the coefficients in the expansion of (3x-1 / x) ^ n is 128, then the sixth term of the expansion is_____ Knowledge of binomial coefficient in Senior High School

Let: x = 1
Then (3 * 1-1 / 1) ^ n = 128, n = 7