Answer:
16.77 m/s, 26.57° south of west
Step-by-step explanation:
The two velocities form a right triangle. Use Pythagorean theorem to find the magnitude of the resultant velocity.
v² = (-15 m/s)² + (-7.5 m/s)²
v = 16.77 m/s
Use trig to find the angle.
tan θ = ((-7.5 m/s) / (-15 m/s))
θ = 26.57° south of west