Answer: Robert's present age is 10 years
Robert father's present age is 40 years
Explanation:
Let r = Robert's current age
Let y = Robert father's current age
Robert's father is 4 times as old as robert. This means that
y = 4x
After 5 years, Robert's father will be three times as old as Robert. This means that
y + 5 = 3(x+5)
y + 5 = 3x + 15 - - - - - - - ;1
We will substitute y = 4x into equation 1. It becomes
4x + 5 = 3x + 15
Collecting like terms,
4x - 3x = 15 - 5
x = 10
y = 4x
Substituting x = 10,
y = 4× 10 = 40 years