b (mod m) is read "a is congruent to b modulo m" and means that m divides a−b.Recall that a b (mod m) is read "a is congruent to b modulo m" and means that m divides a−b.
Another way to say this is that a is congruent to b modulo m if both a and b have the same remainder when divided by m.
Question: What value(s) of x will satisfy 2x 3 (mod 7)?
(answer)