Question

Two books and a pen cost of Rs.18 and two pens and a book cost Rs.15. Find the cost of a book?​

Answer 1

ANSWER !!

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Let the cost of 1 book be ₹ x

Let the cost of 1 pen be ₹ y

Equation 1

2x + y = 18

Equation 2

x + 2y = 15

Now,

Now,Multiplying Eq ( 1 ) by 2 on both sides, we get

=> 2x ( 2 ) + y ( 2 ) = 18 ( 2 )

=> 4x + 2y = 36 ----------- ( Eq 3 )

Then,

Subtracting Eq ( 2 ) from Eq ( 1 ), we get

4x + 2y = 36

x + 2y = 15

=> 3x = 21

=> x = 7

Now,

x + 2y = 15

=> 7 + 2y = 15

=> 2y = 15 - 7

=> y = 8/2

=> y = 4

ANS )

> The cost of 1 book is ₹ 7

> The cost of 1 pen is ₹ 4

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Thanks !!

Answer 2

Answer:

the cost of a book is 7

Step-by-step explanation:

Let the cost of a book x

let the cost of a pen be y

2x+y=18-1equation

x+2y=15-2equation

from 2 equation

x=15-2y

put the value of x in equation 1 we get

2(15-2y) +y=18

30-4y+y=18

-3y=-12

y=4

x+2y=15

x+2(4) =15

x=15-8

x=7

therefore the cost of book =7