Find, by any method, a complete set of solutions for these congruences:

(a) 4x 5 mod 7;

(b) 8x 12 mod 19;

(c) 12x 3 mod 4;

(d) 45x 75 mod 100;

(e) 111x 112 mod 113;

(f) 140x 133 mod 301.