(d) \(\frac{a}{3}.\)
ax . ay . az = (x + y + z)x + y + z
⇒ ax + y + z = (x + y + z)x + y + z
⇒ a = (x + y + z)
Now, (x + y + z)y = ax (given)
⇒ (x + y + z)y = (x + y + z)x ⇒ y = x
Similarly, y = z and z = x.
∴ x = y = z = \(\frac{x+y+z}{3}\) = \(\frac{a}{3}.\)