Joel needs to buy some blank DVDS and zip disks to back up a large amount of data that has been generated by an accounting firm.
He buys 6 DVDS and 3 zip disks for $96. He later realised these are not sufficient and so guys another 5 DVDS and 4 zip disks for $116. How much did each DVD and each Zip disk cost? (Assume the rate per item was changed for each visit). Show working.
