Question

cost of a pen is two and half times the cost of a pencil.express this situation as a linear equation in two variables

Answer 1

let
cost of pen-x
cost of pencil-y
x=5/2y

Answer 2

     1
2 ------ 
      2 

= 5/2

let the cost of pencil be y
let the cost of pen be x

x = 5/2 y

x - 5/2y = 0