Question

the total cost of 6 books and 7 pens is 79 rupees and the total cost of 7 books and 6 pens is 77 rupees. find the cost of 1 book and 2 pens.

Answer 1

Let the cost of the book be x
And the cost of pen be y
Then the cost of 6 books n 7 pens is
6x+7y = 79
And 7x+6y = 77
Now let us add both equations
13x + 13y = 156
X+y = 12
Let us subtract both equations
-x + y = 2
Now let us add the equations so obtained then
X-x + y +y = 12 + 2
2y = 14
y = 7
Substitute in one equation then
X + 7 = 12
X = 5
So the cost of one book is 5
And one pen is 7
So the cost of 1 book and 2 pens is
X + 2y = 5 + 2(7) = 5 + 14 = 19