A pen cost 2/5 as much as a notebook. Raj spent $58.05 to buy 22
pens and 17 notebooks. Find the cost of 25 notebooks.
let the cost of notebooks equal x, and notebooks be 2/5x
set up an equation using x, 17, 25, 2/5x, and 58.05 (dollars), if you don't understand i can give further advice