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5 years hence, the age of Jacob will be 3 times that of his son.5years ago, Jacob's age was 7 times that of his son. What are their present ages?
 Let present age of Jacob  = x years
And  present Age of his son is  = y years
Five years hence,
Age of Jacob   = x + 5 year
Age of his son   = y + 5 year
Given that the age of Jacob will be three times that of his son
x + 5 = 3(y+5)
Add 5 both side we get
x = 3y + 15 - 5
x  = 3y + 10                    … (1)
 Five years ago,
Age of Jacob   = x - 5 year
Age of his son     = y - 5year
 Jacob’s age was seven times that of his son
x – 5   = 7(y -5)
Plug the value of x from equation (1)  we get
3y + 10 – 5  = 7 y – 35
3y + 5          = 7y – 35
3y – 7 y       = - 35 – 5
-4y  =  - 40
y     = - 40 / - 4
y    = 10 year
Put the value of y in equation first we get
x   = 3* 10 + 10
x  = 40 years
Present age of Jacob is 40 years
Present age of Son is 10 years


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