Let John's age be represented as 'x' years, and his father's age be represented as 'y' years.
Given conditions:
John's father is three times the age of John: y = 3x.
Five years ago, the father's age was four times John's age at that time: (y - 5) = 4(x - 5).
We'll solve the system of equations to find their present ages.
Substitute y = 3x from the first condition into the second condition:
(3x - 5) = 4(x - 5).
Expand and simplify the equation:
3x - 5 = 4x - 20.
Move all the terms involving 'x' to one side of the equation:
3x - 4x = -20 + 5.
Simplify:
-x = -15.
Multiply both sides of the equation by -1:
x = 15.
Substitute x = 15 into the first equation to find the father's age:
y = 3(15) = 45.
Therefore, the present age of John is 15 years, and the present age of his father is 45 years.
