Answer: 1.0 m/s2
Step-by-step explanation:
This is a Newton's 3rd Law of Motion problem. The force applied on the box by the skater must equal the force applied on the skater by the box (and in the opposite direction). F = ma
Let x = acceleration of the skater
(15.0 kg)(4.0 m/s2) = (60.0 kg) (x)
x = 60 N / 60 kg = 1.0 m/s2