Question

Five years ago Jacobs age was 7 times that of his son and five years later the age of Jacob will be 3 times of his son. What are their present age?
By elimination method pls solve on paper and send fast guys

Answer 1

Answer:

Let the Jacobs age be X

And his sons age be y

After 5 years Jacobs age will be (X+5)

And his sons age will be (Y+5)

By condition 1:

(X+5)=3(Y+5)

X+5=3Y+15

3Y-X+10=0 .......(1)

Before5 years Jacobs age will be (X-5)

And his sons age will be (Y-5)

By condition 2:

(X-5)=7(Y-5)

X-5=7Y-35

7Y-X-30=0 ......(2)

X=3Y + 10 .......from (1)

Substituting the value of X in equation (2)

7Y-(3Y+10)-30=0

7Y-3Y-10-30=0

4Y = 40

Y= 10

Substituting the value of Y in equation 1.

3(10) - X+ 10=0

X=40

THEREFORE the age of Jacob =40 years

And age of his son = 10 years

Step-by-step explanation:

Answer 2

Answer:

The present age of Jacob is 40 years.

And the present age of son of Jacob is 10 years.

Step-by-step-explanation:

Let the present age of Jacob be x years.

And the present age of son of Jacob be y years.

Five years ago,

The age of Jacob = ( x - 5 ) years

And the age of his son = ( y - 5 ) years

From the first condition,

( x - 5 ) = 7 ( y - 5 )

⇒ x - 5 = 7y - 35

⇒ x - 7y = - 35 + 5

⇒ x - 7y = - 30 - - ( 1 )

Now,

Five years later,

The age of Jacob = ( x + 5 ) years

And the age of his son = ( y + 5 ) years

From the second condition,

( x + 5 ) = 3 ( y + 5 )

⇒ x + 5 = 3y + 15

⇒ x - 3y = 15 - 5

⇒ x - 3y = 10 - - ( 2 )

By subtracting equation ( 1 ) from equation ( 2 ), we get,

x - 3y = 10 - - ( 2 )

-

x - 7y = - 30 - - ( 1 )

(-).....(+).......(+)

______________

⇒ 4y = 40

⇒ y = 40 ÷ 4

⇒ y = 10

By substituting y = 10 in equation ( 2 ), we get,

x - 3y = 10 - - ( 2 )

⇒ x - 3 ( 10 ) = 10

⇒ x - 30 = 10

⇒ x = 10 + 30

⇒ x = 40

Now,

The present age of Jacob ( x ) = 40 years.

And the present age of son of Jacob ( y ) = 10 years.