I just figured it out. Sorry!
The minimum speed that the motorcyclist needs to be at in order to not fall straight down is when n=w. Therefore since n+w=mv^2/r, and n=w, then we can just say that n+w=2w.
1. A motorcyclist in the Globe of Death, pictured at the start of the
chapter, rides in a 2.2-m-radius vertical loop. To keep control of
the bike, the rider wants the normal force on his tires at the top of
the loop to equal or exceed his and the bike's combined weight.
What is the minimum...