let

m = the age of the man now

s = the age of the son now

5 years ago a man was 7 times as old as his son

m - 5 = 7(s - 5)

after 5 years he will be thrice as old as his son

m + 5 = 3(s + 5)

by solving the system of equations

m - 5 = 7(s - 5)

m + 5 = 3(s + 5)

we find

m = 40 years

s = 10 years

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the man is 40 years old now.

the won is 10 years old now.