Here are videos on how to beat ninja exam from 117-120 pretty easily but you made need certain ninjas to beat it. These teams do not rely on RNG and will only take a few tries.
https://www.youtube.com/watch?v=Uh3b29xW0rQ&list=PLmtsSNi3Y-N5P9cA4SjFOsU89hv46bmBY