Solve the three-variable system of equations. (Mathematics)

3x + 7y + 6z = -20
x - 3y + 2z = - 6
2x + 5y + 5z = -16
a) x = -2, y = 4, z = 3
b) x = 3, y = -2, z = 4
c) x = 4, y = 3, z = -2
d) x = -4, y = -3, z = 2