You can put this solution on YOUR website! Five years ago, John's age was half the age of mary. John is 4 years younger than Mary now. How old is John?
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Hint: how old were they 5 years ago?
Five years ago John was (still; as always) 4 years younger than Mary and he was half of her age ====>
hence, his age then was 4 years, while Mary's age was 8 years at that time.
It means that now John is 4 + 5 = 9 years old, while Mary is 8 + 5 = 13 years old.
