Question

5 books and 7 pens together cost 79 where as 7 books and 5 pens together cost 77. find total cost of 1 book and 2 pens

Answer 1

Hi friend.. here is ur answer

Suppose the cost of 1 book is = x rs.

and, cost of one pen is = y rs.

According to the question,

5x + 7y = 79

or, 5x x 7 + 7y x 7 = 79 x 7

or, 35x + 49y = 553........................(1)

Anew,

7x + 5y = 77

or, 7x x 5 + 5y x 5 = 77 x 5

or. 35x + 25y = 385......................(2)

(1) - (2)

or, 24y = 168

or, y = 7

so, 5x + 7 x 7 = 79

or, 5x = 30

or, x = 6

So, total cost of one book and one pen is-

= (x+y)

= 7 + 6 Rs.

= 13 Rs

Hope this helps and mark as brainliest please

Answer 2

Let,
x be the the cost of book
y be the the cost of pens.

A. T. Q. (According to condition),

5x+7y=79 ....(1)
7x+5y=77 ....(2)

First do addition then subtraction then you will get again two equation and add them so then put the value of x in the equation and you will get the value of y.

And count the value and add them.