Solve the following question given below:
Question: You have built a homemade skate board for your nephew out of a plank and a set of wheels. Your nephew speeds up to a final speed of 2 m/s on level ground. Your nephew throws himself backward off the skateboard, kicking the rickety skateboard forward at 7 m/s. Your nephew has a mass of 65 kg and the skateboards mass is 9 kg.
Part A: How fast was your nephew moving when his feet left the skateboard?
Please show work thank you!