Question

Solve the congruence 9x 17 (mod 26).

Answer 1

We have $17\equiv-9\pmod{26}$, so that $x\equiv-1\pmod{26}$, so $x\equiv25\pmod{26}$, and any solution of the form $x=25+26n$ satisfies the congruence, where $n$ is any integer.