Let us assume the present age of men be x years

Also, the present age of his son be y years

According to question, after 5 years:

(x + 5) = 3 (y + 5)

x + 5 = 3y + 15

x – 3y = 10 …(i)

Also, five years ago:

(x – 5) = 7 (y – 5)

x – 5 = 7y – 35

x – 7y = – 30 …(ii)

Now, on subtracting (i) from (ii) we get:

– 4y = – 40

y = 10

Putting the value of y in (i), we get

x – 3 × 10 = 10

x – 30 = 10

x = 10 + 30

x = 40

∴ The present age of men is 40 years

Hence, option D is correct