Question 1101298

J = M-3  (1)
F = M-4   (2)
M + F + J = 29  (3)
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Substituting for J and F (one could go directly to the next step using the wording from the problem):
M + (M-4) + (M-3) = 29 

3M - 7 = 29
3M = 36
 M = 12  —> J = 9   and  F = 8

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Ans: Mike is 12, Joe is 9, and Fred is 8.
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Check:  12+9+8 = 21+8 = 29