I've been trying to solve an online challenge. I've been given a file, which I suspect is encrypted (around 15KiB). I've also managed to obtain what seems to be an RSA private key (n == 2048). I know that RSA wasn't used to encrypt the whole file since from what I've read, given that n = 2048, the maximum data size it can encrypt is 245 bytes.
What are my options here? I've read that usually large files are encrypted using a symmetric encryption algorithm and that RSA is used to encrypt the symmetric key.
Given that I only have the encrypted file and the private RSA key, what is my best course of action to try and decrypt the file? Are there any common techniques here?