SOLUTION: John is twice as old as Sarah. Three years from today, the sum of their ages will be 42. How old is John today?

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Question 387120: John is twice as old as Sarah. Three years from today, the sum of their ages will be 42. How old is John today?

Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
j = 2s,
j+3 + s+3 = 42, or j + s = 36. Substituting the 1st equation into the last equation, we get 2s + s = 36, or 3s = 36, or s = 12, the age of Sarah now, and j = 2s = 24, the age of John.