Question

Five years from now, a father's age will be tree times his son's age, and 5 years ago, he was seven times as old as his son was. What are their present age?

Answer 1

The answer is "10 and 40".

Explanation:

`\to f + 5 = 3(s + 5) = 3s + 15\\\\\to f - 5 = 7(s - 5) = 7s - 35\\\\`

Subtracting the equations to get

`\to 10 = -4s + 50\\\\\to -40 = -4s\\\\\to s = (40)/(4) \\\\\to s=10\\\\\to f = 40\\\\`

So the Son age is 10, and the father's age is 40.