which divides 380.

Hence there are 5 incongruent solutions (algebraists say a solution in each equivalence class).

You can solve this with a techinque but because the numbers are small we can try to "guess" what the solution is. First simplify the 380, the remainder it leaves it 30.

Thus,

.

We can see that is surly a solution.

By a theorem all other solutions are,

Thus,

Which are,