Problem 15.2 In each case, solve the systems of equations by finding the inverse of the coefficient matrix.

3x - y = 5
2x + y + 2z = 0
x - 2y + 4z = -2

a. x = 1, y = 2, z = -1
b. x = 2, y = -1, z = 3
c. x = -1, y = 3, z = 2
d. x = 3, y = -2, z = 1