Answer:
100000 m/s in the opposite direction
22369.4185194 mph
Step-by-step explanation:
= Mass of superhero
= Mass of asteroid =

= Speed at which the asteroid is thrown = 100 m/s
= Recoil velocity
Here the linear momentum of the system is conserved

The recoil speed is 100000 m/s in the opposite direction
Converting to miles per hour

The speed is 22369.4185194 mph