Five years ago a man was seven times as old as his son. Five years hence, the father will be three times as old as his son. Find their present ages.

Explanation

Let age of father is `x` years and age of the son is `y` years.

Then,

`x-5 = 7(y-5)`

`=> x-5 = 7y-35`

`=>x-7y = -30->(1)`

Also,
`x+5 = 3(y+5)`

`=>x+5 = 3y+15`

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