With the random numbers generated, can I know which RNG seed was used?
If the RNG is cryptographically strong, then you should not be able to do any better than the naive brute force: try each seed until you get matching random numbers.

If this is a homework question, then I would guess that either they used a very small seed (like "3" or "15"), or the RNG is not cryptographic strength and with some time analyzing the linear congruence algorithm, you might see how to invert it.