solve the equations by using

Question

a) the adjoint matrix
b) elementary row operations

i) x+y+z=6
2x-y+z=3
x+4y-z=6

ii) 3p-3q+r=1
-3p+5q-2r=-1
p-2q+r=3

iii)-12a+b+17c=-14
2a-b+3c=5
8a+b-13c=-3

thanks sir/madam