Answer the following question:

Please check the solution you get by using cross multiplication method. 

 

You should get A/-7=B/8=C/-3=k and not A/-7=B/8=C/3=k (It has to be C/-3). And if you will correct for that, then you will get the right solution. 

 

You will get C/-3 by C/(3*1 - 3*2) = C/-3 . Please check this.