  To each i, j belonging to some set of integers, attach the integer a(i,j).
Are there integers x(i) such that x(j)-x(i) is congruent to a(i,j) mod (i,j)? A
necessary condition is that a(i,j)+a(j,k) be congruent to a(i,k) mod (i,j,k).
This condition is sufficient.
