Find all possible solutions for x such that △ABC is congruent to △DEF. One or more of the problems may have no solution.

16. △ABC: sides of length 6, 8, and x. △DEF: sides of length 6, 9, and x - 1.

17. △ABC: sides of length 3, x + 1, and 14. △DEF: sides of length 13, x - 9, and 2x - 6

18. △ABC: sides of length 17, 17, and 2x + 1. △DEF: sides of length 17, 17, and 3x - 9

19. △ABC: sides of length 19, 25, and 5x-2 △DEF: sides of length 25, 28, and 4 - y