Question 708112:  Kathy is 20 years older than Carol. In 6 years, the sum of their ages will be 50. How old is each now? 
 Answer by josgarithmetic(39630)      (Show Source): 
You can  put this solution on YOUR website! k and c for kathy's age and carol's age NOW.
 
 
Now: k=c+20, which becomes k-c=20.
 
Six Years from Now:  (k+6)+(c+6)=50, from which 
k+c=50-12, 
k+c=38.
 
 
You have this system to solve: 
k-c=20, and k+c=38.
 
Various few simple ways to continue.  Try k=c+20, one of the original equations, and substitute into k+c=38..., solve for c... 
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