A man is 9 times older than his son, 15 years later he will be only thrice as old as his son. What is man's present age?

If x is the son's age,

9x+15 = 3(x+15)

To solve this problem, we can set up equations and solve them algebraically.

Let's assume the present age of the son is x.
According to the given information, the man is 9 times older than his son: man's age = 9x.

After 15 years, the son's age will be x + 15, and the man's age will be 9x + 15.
The problem states that 15 years later, the man will be only thrice as old as his son, so we can set up the equation: 9x + 15 = 3(x + 15).

Now, let's solve this equation step-by-step:

Expanding the equation:
9x + 15 = 3x + 45

Combining like terms:
9x - 3x = 45 - 15
6x = 30

Dividing both sides by 6:
x = 5

Therefore, the son's present age is 5 years old. Since the man is 9 times older than the son, the man's present age would be 9 x 5 = 45 years old.