Question

5 years hence the age of Jacob will be 3 times that of his son 5 years ago Jacobs age was 7 times that of his son what are their present ages

Answer 1

his son. What are their present ages?

Let        present age of Jacob                     = x year

And      present Age of his son is             = y year

Five years hence,

Age of Jacob will                              = x + 5 year

Age of his son will                                       = y + 5year

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 will                              = x - 5 year

Age of his son will                                       = 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

Plug the value of y in equation first we
x          = 3* 10 + 10

x          = 40 years

therefore
age of Jacob =40 years and
age of his son=10 years

Answer 2

Let the present age of Jacob be x and of his son be y.
After 5 years
(x+5)=3(y+5)
5 years before
(x-5)=7(y-5)
Solving it
We get
3y+15-5=7y-35+5
3y+10=7y-30
4y= 40
y = 10
And hence
x= 40
So age of Jacob is 40 yrs and of his son is 10 yrs.