This question is based on law of conservation of momentum, which says total total momentum of the system is equal to total momentum of the system after collision.
Before collision, = 340 kg m/s
After collision, = mass * velocity = 60 kg * v
Here, we need to find the velocity with which Sheila was thrown after the collision.
According to law of conservation of momentum,
=
340 = 60 * v
v = 340 / 60 = <u>5.667 m/s</u> [approximately]
The speed with which Sheila was thrown from the bike is <u>5.667 m/s</u>.