Needing to see a solution to de is congruent to 1 mod phi of pq. pq needs to be > 9875040
Have you tried doing this yourself? There is some time involved, but the procedure itself is not too difficult, probably the hardest parts are finding a modular inverse (when solving ), and then modular exponentiation for encrypting and decrypting. Please show some work and let us know where you are getting stuck, also please tell us whether you're allowed to use a computer algebra system (CAS) like PARI/GP or Mathematica, or if you need to do everything by hand, or with a pocket calculator, etc.