If the reflection of the point P(1,0,0) in the line x−12=y+1−3=z+108 is (a,b,c) then |a+b+c|7=

Let M be the midpoint of PQ and AM=r⇒M(1+2r,−1−3r,−10+8r)Since AM¯⊥PM ¯, we have AM¯.PM ¯=0⇒r=1⇒M(3,−4,−2)∴Q=(a,b,c)=2M−P=(5,−8,−4)∴|a+b+c|7=|5−8−4|7=77=1