Given lines are 1x−6=0y−4=3z−8 and 2x−5=−3y−1=6z−5.
Let, AB be a line parallel to 2x−5=−3y−1=6z−5 which intersects 1x−6=0y−4=3z−8 at point B, where A≡(7,−2,11)

So, equation of AB is,
2x−7=−3y+2=6z−11=λ(let)
⇒x=2λ+7,y=−3λ−2,z=6λ+11
⇒B≡(2λ+7,−3λ−2,6λ+11)
Also, the point B lies on 1x−6=0y−4=3z−8.
⇒12λ+7−6=0−3λ−2−4=36λ+11−8
⇒−3λ−2−4=0
⇒−3λ=6
⇒λ=−2
⇒B≡(3,4,−1)
⇒AB=(7−3)2+(4+2)2+(11+1)2
⇒AB=16+36+144
⇒AB=196
⇒AB=14