A man is four times as old as his son. In five years time he will be three times as old. Find their

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A man is four times as old as his son. In five years time he will be three times as old. Find their present ages.

Let the man's age be m, and the son's age be s. We have:

1. m = 4s
2. m + 5 = 3(s + 5)

Substitute (1) into (2)
4s + 5 = 3s + 15

Use our equation calculator, and we get s = 10.
m = 4(10)
m = 40