One pencil costs Rs 2 and one fountain pen cost Rs 15. [[1]] is the cost of x pencils and y fountain pens.

 

Cost of one pencil = Rs 2

Cost of one fountain pen = Rs 15

Cost of x pencils = 2x

Cost of y fountain pens = 15y

So the cost of x pencils and y fountain pens = Rs (2x + 15y)

Hence, the cost of x pencils and y fountain pens is Rs (2x + 15y).