Answer is (D) 336
Since all three given vectors are coplanar, we get
Adding Eqs. (2) and (3), we have
2x + 2z = 24
x + z = 12 (4)
Now, substituting the value of y from Eq. (2) and value of x from Eq. (4) in Eq. (1), we get
24 – 2z + 3 (24 – z) – z = 0
That is, 96 = 6z
⇒ z = 16
and hence x = −4 and y = 8.
Therefore,