Mark M. answered 10/15/21
Retired math prof. Very extensive Precalculus tutoring experience.
f(x) = x7 - 3 has degree 7, so there are a total of 7 roots including any repetitions or complex numbers.
f(x) has 1 sign change, so the number of positive real roots is 1.
f(-x) = (-x)7 - 3 = -x7 - 3. Since there are no changes in sign, there are no negative real roots.
So, there are 6 complex roots, 1 positive real root, and no negative real roots.