Question

Vector A points in the negative x direction. Vector B points at an angle of 29.0 above the positive x axis. Vector B has a magnitude of 17m and points in a direction 46.0 below the positive x axis.
Given that A+B+C=0
Find magnitude of A and B

Answer 1

You need to know Vector C, or the magnitude of A, to answer that question.

You specified B twice, in a contradictory manner.

I believe you copied the problem incorrectly.

Answer 2

I believe the second vector B is supposed to be vector C.