SOLUTION: Carla is three times as old as John. Four years from now, Carla’s age will be half that of John’s. Find their present age.

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Question 1122431: Carla is three times as old as John. Four years from now, Carla’s age will be half that of John’s. Find their present age.
Answer by Alex.33(110) About Me  (Show Source):
You can put this solution on YOUR website!
Use their name initials to represent their age.
C=3J
C+4=(J+4)/2
substitute C in the second equation:
3J+2=J/2. It indicates that 3J is 2 less than J/2. Impossible.

So I'm assuming that 'Carla’s age will be half that of John’s' actually should be 'John's age will be half of Carla's'.
C=3J
(C+4)/2=J+4
Solve for C and J:
C=12
J=4