Expert: Richard J. Raridon - 6/30/2009

Question
find abc if (ab+3c)=12 and (ab-3c)=4

Answer
Since you have only two equations you will have multiple answers.  
Add the two equations together and you get 2ab = 16 so ab = 8 and therefore, 3c = 4.  That gives you c = 4/3 but a and b can be any combination such that ab = 8.  could be 1 and 8, 2 and 4, 0.5 and 16, etc.