The given lines are $\frac{x-1}{-3}=\frac{y-2}{2k}=\frac{z-3}{2}$...(1) and $\frac{x-1}{3k}=\frac{y-1}{1}=\frac{z-6}{-5}$ ...(2) The direction ratios of line (1) are < –3, 2k, 2 >The direction ratios of line (2) are < 3k, 1, –5 >The line (1) and (2) are perpendicularif (–3) (3k) + (2k) (1) + (2) (–5) = 0if – 9k + 2k – 10 = 0 if 7k = –10 if $k = -\frac{10}{7}$