Don't know what the triple horizontal line means. Where did you see it?
11.13 is alternate notation for 11*13. 143 is 11 multiplied by 13, and it looks like it's a clue to help you solve the problem.
Mod is short for modulo and is the remainder after dividing by that number. So for example 17 mod 10 is 7, and if one of the problem solutions is, say, 146, then 146 mod 143 is 3, so the answer would be 3. I imagine there will be an infinite number of solutions, and that mod 146 there are only 4 (so the solutions are a+146n, for four values of a, and n=0,1,2....)