Two lines and

are perpendicular to each other if

a₁a₂ + b₁b₂ + c₁c₂ = 0

Given -

comparing with

we get -

x₁ =1, y₁ = 2, z₁ = 3

& a₁ = - 3, b₁ = 2k, c₁ = 2

Similarly,

comparing with

we get -

x₂ = 1, y₂ = 2, z₂ = 3

& a₂ = 3k, b₂ = 1, c₂ = -5

Since the two lines are perpendicular,

a₁a₂ + b₁b₂ + c₁c₂ = 0

⇒ (-3) × 3k + 2k × 1 + 2 × (-5) = 0

⇒ -9k + 2k - 10 = 0

⇒ -7k = 10

∴ k = -10/7

Hence, the value of k is -10/7.