(i) let c = 273x + 23 (mod 1155). find two different values of that yield the same value of c.

(ii) explain why c does not have a decoding function.

Hello, do I simply guess the 2 different values that gives the same results for c? How will I know if they are the right numbers that gives the same result for c?

Why this one doesn't have a decoding function? I already got the inverse for 273 (mod 1155), and unfortunately it doesn't have an inverse. Please kindly explain and hopefully get some step-by-step solution. Thank you!