The system of equations $x + y + z = 6, 2x + y + z = 7, x + 2 y + z = 8$ has

Ax = b has a unique solution if and only if rank[A] = rank[A|b] = n where n is number of unknown variables

x + y + z = 6, 2x+ y +z = 7, x + 2 y +z = 8

we can also find it using Rank

rank[A] = rank[A|b] = 3

hence unique solution

Option a