We consider the system of equations in GF( f = 1, · · · > 7\ are independent identically distributed random variables taking the values 1,...,N with equal probabilities, the coefficients <2j ,... ,α£ , t = 1,... ,Γ, are independent identically distributed random variables independent of /i(r),... ,//·(/), ί = 1,... ,Γ, and taking the non-zero values from GF( a. Then for any fixed integers r > 3 and q > 3 there exists a constant oc r such that ES(A r ) -> 0 if a < oc r , and ES(A r ) -> <*> if a > cc r .The research was supported by the Russian Foundation for Basic Research, grants 96-01-00338 and 96-15-96092.We recall the notion of critical sets which was introduced in [3] (see also [1,2]) for the field GF(2) and extended to finite fields in [5].We consider a Γ χ TV matrix A = \\a t j\\ in the finite field GF(q) with q elements and denote its rows by a t = (a t \,...,a tN ], t = Ι,.,.,Γ.The rows with numbers t\,...,t m and weights 81 . . . , e m taking non-zero values from GF(qr) form a critical set Β -{t\ , . . . , t m \ ε\ , . . . , e m } if the sum is the zero vector.For critical sets we define the multiplication by a non-zero α G GF(q) setting for5 = {ii,.