Question

could you please explain me how 3 came in 11 question

Answer 1

its not clear please upload pic clearly
its quite hazy

Answer 2

see in Numerator part...where you have Dot product of Vector P and Unit vector i...

where Vcetor P = 3i - 6j + 2k
Now
( Vector P) . i = ( 3i - 6j + 2k ) . i
=( 3i . i ) -( 6j . i )+ ( 2k . i )
= 3 x ( i.i) - 6 (j.i) + 2 (k.i)
Note : i.i = j.j = k.k = 1 and
i.j = j.i= 0 , j.k = k.j = 0 , k.i = i.k = 0
( Vector P) . i = 3 × 1 - 6 × 0 + 2 × 0 = 3 + 0 + 0 = 3