P + P + O = 14
N + N + M = 20
O + M + P = 12
P + M + N = 18

Find O.

Answer :

We have  :

P + P + O = 14                         ----- ( 1 )

N + N + M = 20                        ----- ( 2 )

O + M + P = 12                        ----- ( 3 )

P + M + N = 18                        ----- ( 4 )

Now we subtract equation 3 from equation 4 , we get

N  -  O =  6 

O  =  N  -  6                             ---------- ( 5 )

And

We subtract equation 4  from equation 2 , we get

N  -  P =  2

P  =  N  -  2                             ---------- ( 6 )

Now we substitute values from equation 5 and 6 in equation ( 1 ) , We get

N  -  2 + N  -  2 + N  -  6 = 14

3N  -  10  =  14

3N  =  24

N  =  8  , Substitute that value in equation 5 , we get

O  = 8 - 6  

O  = 2                                                                       ( Ans )