The cost of 5 pens and 8 pencils is ₹ 120, while the cost of 8 pens and 5 pencils is ₹ 153. Find the cost of 1 pen and that of 1 pencil.

Explanation

Let the cost of 1 pen be ₹ x and that of 1 pencil be ₹ y. Then,
` 5x + 8y = 120 " " `… (i) and ` 8x + 5y = 153" " `… (ii)
Adding (i) and (ii) , we get ` 3(x - y ) = 273 rArr x + y = 21" " `... (iii)
Subtracting (i) from (ii), we get ` 3 ( x - y ) = 33 rArr x - y = 11" " `... (iv)
From (iii) and (iv), we get ` x = 16 and y = 5`.