how to solve linear equations involving modulo?

In one of my p开发者_Go百科rojects, I encountered a set of linear eqns. with modulo. I am putting it in simple format with only 2 variables,

(a11x + a12y) mod 8 = b1

(a21x + a22y) mod 8 = b2

In case of simple eqns. with out modulo I can use: AX=B, X=inv(A)*B. But how to handle this modulo? Any clue or pointers will be very helpful.