from: category_eng 
1. 


2. 


3. 


1. e  
2. E 
Many Variables 
the range of x is limited.  
3. b 
Modification 
Eliminate a variable.  
a/c = 2/3 let say a=2k and c=3k (k is integer) then bk = 7, b= 7/k but 7/k >1 so.. k<7.. so k=1 b=7, a=2, c=3 