Answer:
5i +(5/3)j - (5/3)k
Step-by-step explanation:
Vector b is in the same direction as vector a, so it is a scalar multiple of a.
b = ca for some positive real number c.
b = c(3i + j - k) = 3ci + cj - ck
|b| = sqrt[(3c)^2 + c^2 - c^2] = sqrt(9c^2) = 3c
If |b| = 5, then 3c = 5 and c = 5/3
That makes b = (5/3)(3i + j - k) = 5i +(5/3)j - (5/3)k
