The sum of three numbers is 19. Two times the first number increased by six times the second number
plus the third number is 12. The sum of three times the first number and eight times the second number,
increased by the third number is -14. If the first number is represented by x, the second number is
represented by y, and the third number is represented by z, which of the systems of equations below can
be used to determine the three numbers?